Good Day to you!

I've been asked to make some topic-wise list of problems I've solved. Even though I couldn't involve all problems, I've tried to involve at least "few" problems at each topic I thought up (I'm sorry if I forgot about something "easy"). I've alredy made such list once anyway I've tried to include more problems now — so here it is:

<spoiler summary="aho">

http://www.spoj.com/problems/ADAJOBS/

URI 2226 (5) //[NICE][NUMBERS][DP]

http://www.spoj.com/problems/SUB_PROB/en/

http://codeforces.com/contest/696/problem/D 8

http://www.spoj.com/problems/AHOCUR/ 5 //Aho-Corassic + DP

https://www.codechef.com/problems/LYRC (5) //Sample aho-brute-force

http://codeforces.com/problemset/problem/346/B //Proposed by [user:bradyawn]

</spoiler>

<spoiler summary="automat">

6861 [LA] //CYK

UVA	10679 //Suffix Automat

http://www.spoj.com/problems/STRMATCH/ //Suffix Automat  &mdash; trie might do too

http://www.spoj.com/problems/NSUBSTR2/ //Suffix Automaton

</spoiler>

<spoiler summary="belman-ford">

UVA	12519

http://www.spoj.com/problems/ARBITRAG/ (4) //Or Floyd-Warshall

</spoiler>

<spoiler summary="bfs">

http://www.spoj.com/problems/ADACYCLE/ [FW]

UVA 13295 (6) //[NICE][EFFICIENCY][IMPLEMENTATION]

http://codeforces.com/gym/101992/problem/H (4) //[VERY NICE][MAX]

http://codeforces.com/gym/100112 [H] (3)

6151 - Beehives (4) //[NICE] //Search for shortest cycle

https://devskill.com/CodingProblems/ViewProblem/60

https://devskill.com/CodingProblems/ViewProblem/150

11312 UVA (3)

11392 UVA (4)

http://codeforces.com/contest/653/problem/E (6)

http://codeforces.com/contest/769/problem/C 5 //FL:ODD/**** | bfs+greed NICE

10968 UVA (3) //EASY + NICE (bfs withot <=2 nodes)

http://codeforces.com/contest/796/problem/D (3) //NICE+EASY ... print visited in bfs (not par)

10888 UVA (4) //VERY NICE &mdash; but not main technique ... ++ DP /or/ MCMF

http://codeforces.com/contest/821/problem/D (5) //VERY NICE &mdash; Consider only points not GRID

http://www.spoj.com/problems/DIGOKEYS/ (4) //Easy [Nice problem &mdash; weird statement]

http://www.spoj.com/problems/SPIKES/ (3) //Easy bfs (# of 's' * 2)

http://www.spoj.com/problems/MULTII/ (4) //VERY NICE: BFS over numbers (K*10+d)%N

http://www.spoj.com/problems/ADV04F1/ (5) //VERY NICE: [imple] ~ N^4*BigConstant

http://www.spoj.com/problems/INVESORT/ (5) //Big limit (really usefull :P)

http://codeforces.com/contest/59/problem/E (5) //[NICE][DOUBLE-STATES][SET]

http://codeforces.com/contest/877/problem/D (4) //[NICE] Add vector to # of states

</spoiler>

<spoiler summary="bfs-grid">

4291 - Sculpture (6) //[NICE][PREPROCESS][NORMALIZE]

10977 UVA (3)

928 UVA (3)

13116 UVA (4)

314 UVA (3)

11487 UVA (4)

5622 LA (7)

11931 UVA (5)

http://www.spoj.com/problems/KNMOVE/ 3 //simple knights

http://www.spoj.com/problems/SERGRID/ 3 //almost classical

http://www.spoj.com/problems/NAKANJ/ 3 //Classical chess &mdash; KNIGHT

http://www.spoj.com/problems/PUCMM223/ (4) //NICE (but not many languages) &mdash; 2 moving [x][y]

http://www.spoj.com/problems/SPIRALGR/ (4) //NICE (not typical) [SIEVE]

http://www.spoj.com/problems/DCEPC706/ (4) //NICE &mdash; travelling outside

http://codeforces.com/contest/35/problem/C (3) //No obstacles [multiple starts]

</spoiler>

<spoiler summary="big">

https://devskill.com/CodingProblems/ViewProblem/394 (2) //Multiplication (or math)

http://codeforces.com/contest/66/problem/A (2) //Big + iffs + implementation

UVA &mdash; 10183

10106 &mdash; Product [UVA]

10523 &mdash; Very Easy !!! [UVA]

787 &mdash; Maximum Sub-sequence Product [UVA]

2871 &mdash; Rhyme Schemes [LA][BELL]

UVA &mdash; 10497

http://www.spoj.com/problems/MUL/en/

http://www.spoj.com/problems/ITRIX_E/

11115 &mdash; Uncle Jack

11448 &mdash; Who said crisis? [UVA]

http://www.spoj.com/problems/GCD2/

10083 &mdash; Division [UVA]

11830 &mdash; Contract Revision [UVA]

1230 &mdash; MODEX [UVA]

http://www.spoj.com/problems/NUMPLAY/

10519 &mdash; UVA

7651 &mdash; Pascal's Hyper-Pyramids [LA]

11344 &mdash; The Huge One [UVA]

10303 &mdash; How Many Trees? [UVA]

http://www.spoj.com/problems/FAST2/

495 &mdash; Fibonacci Freeze [UVA]

10023 &mdash; Square root [UVA]

http://www.spoj.com/problems/SKYLINE/

http://www.spoj.com/problems/NITT2/

11879 &mdash; Multiple of 17

http://www.spoj.com/problems/MINNUM/

10494 &mdash; If We Were a Child Again [UVA]

10013 &mdash; Super long sums [UVA]

10925 &mdash; Krakovia [UVA]

10814 &mdash; Simplifying Fractions [UVA]

619 &mdash; Numerically Speaking [UVA]

713 &mdash; Adding Reversed Numbers [UVA]

1226 &mdash; Numerical surprises [UVA]

623 &mdash; 500! [UVA]

http://codeforces.com/problemset/problem/18/D

http://www.spoj.com/problems/NUMTSN/

https://www.codechef.com/problems/FRJUMP

10220 &mdash; I Love Big Numbers ! [UVA]

https://www.hackerrank.com/contests/projecteuler/challenges/euler025

https://www.hackerrank.com/contests/projecteuler/challenges/euler020

11645 UVA 4

Gym &mdash; 100866A [ACM ICPC 2005–2006 NEERC Moscow Subregional Contest]

CSQUARE [SPOJ]

http://www.spoj.com/problems/PARCARD1/

10070 &mdash; Leap Year or Not Leap Year and .. [UVA]

http://www.spoj.com/problems/SOLDIERS/

12333 &mdash; Revenge of Fibonacci [UVA]

http://www.spoj.com/problems/NDIVPHI/

http://www.spoj.com/problems/IWGBS/ [UVA]

http://www.spoj.com/problems/POP3/ [Prime-Test]

http://www.spoj.com/problems/VGCD/

http://www.spoj.com/problems/NDIVPHI2/

12924 &mdash; Immortal Rabbits [UVA]

Count the Trees  [UVA][10007]

10198 &mdash; Counting [UVA]

11375 UVA 3

http://www.spoj.com/problems/MINNUM/ 3 // BIG/9+!!(BIG%9)

10844 UVA 4 //Bell numbers + big (might be slightly slow!)

http://www.spoj.com/problems/NITT2/ 2 //Divisibility by two constants

http://www.spoj.com/problems/NUMPLAY/ (3) //With DP

http://www.spoj.com/problems/IWGBS/ (3) //Fibonacci 10^4

http://www.spoj.com/problems/PUCMM025/ (2) //Divisibility by 1 → 9

http://www.spoj.com/problems/CSQUARE/ (3) //Converse + Power

http://codeforces.com/contest/17/problem/D (5) //B^(N-1)*(B-1)%C [B/N are big]

</spoiler>

<spoiler summary="binary_search">

https://codeforces.com/contest/1169/problem/C (3) //[NICE]

https://codeforces.com/contest/1173/problem/C (4) //[NICE]

https://codeforces.com/contest/1201/problem/C (4) //[NICE][SIMPLE]

https://codeforces.com/contest/1183/problem/C (3) //[SIMPLE][NICE]

http://codeforces.com/gym/101628/problem/J (4) //[NICE][EASY]

http://codeforces.com/gym/101962 [F] (5) //[NICE][FW]

http://codeforces.com/contest/920/problem/G (5) //[NICE][MATH][IE]

http://codeforces.com/contest/140/problem/C (4) //[NICE][GREEDY]

http://codeforces.com/contest/898/problem/E (4) //[NICE][SIMPLE][PREPROCESS]

http://codeforces.com/contest/888/problem/C (3) //Can be done without BS

http://codeforces.com/contest/68/problem/B (3) //[EASY][DOUBLE]

http://codeforces.com/contest/42/problem/A (2) //Or simple math

http://codeforces.com/contest/883/problem/I (4) //[NICE][SET][2Pointers]

http://codeforces.com/contest/51/problem/C (4) //[NICE][GREEDY-CHECK]

http://codeforces.com/contest/729/problem/C 3

http://codeforces.com/contest/714/problem/D 8

13150 (UVA) 4

http://codeforces.com/contest/749/problem/D 5

11692 (UVA) 4

11516 (UVA) 3

http://codeforces.com/contest/760/problem/B 3

http://codeforces.com/contest/675/problem/D 4 //dunno &mdash; solvable with treap

http://www.spoj.com/problems/NDS/ 4 //BS over LIS

http://www.spoj.com/problems/VECTAR4/ 3

http://codeforces.com/contest/767/problem/D 4 //NICE

http://codeforces.com/contest/627/problem/D (7) //with dp &mdash; NICE

http://codeforces.com/contest/779/problem/D (3) //NICE + EASY

http://www.spoj.com/problems/CNTINDX/ (4) //Map+BS === OK

13177 UVA (3) //BS over answer == OK

http://codeforces.com/contest/801/problem/C (3) //BS + SUM -EASY

http://codeforces.com/contest/803/problem/D (3) //BS by answer

http://codeforces.com/contest/807/problem/C (3) //Or math

http://codeforces.com/contest/818/problem/F (4) //NICE &mdash; Live VS Clique

http://codeforces.com/contest/845/problem/E (5) //VERY NICE &mdash; min(X,Y) .. add time, repeat

http://www.spoj.com/problems/MATHLOVE/ (2) //BS + Gaus (or otter ways)

http://www.spoj.com/problems/SABBIRGAME/ (3) //Binary search over answer ::max(0,ANS)

http://codeforces.com/contest/846/problem/D (4) //BS+Precalculation OR 2D-RMQ

http://www.spoj.com/problems/RPLC/ (3) //Classical

http://www.spoj.com/problems/TRIGALGE/ (2) //On doubles &mdash; simple function given

http://www.spoj.com/problems/ABA12E/ (4) //VERY NICE &mdash; BS on answer + 2Pointers

http://codeforces.com/contest/847/problem/E (4) //NICE: Back+Front OR Front+Back

http://www.spoj.com/problems/MAIN8_C/ (3) //Classical &mdash; simultion over array

http://www.spoj.com/problems/FUNFACT/ (4) //VERY NICE &mdash; Sterling Approximation

http://codeforces.com/contest/16/problem/C (3) //[or math][simple formula check]

http://codeforces.com/contest/21/problem/C (3) //[NICE][prefix-sum+lower_bound]

http://codeforces.com/contest/24/problem/E (5) //[doubles]

http://codeforces.com/contest/875/problem/E (6) //VERY NICE [BS][Keep possible places]

</spoiler>

<spoiler summary="bits">

https://codeforces.com/contest/1204/problem/A (2) //[POWERS]

https://codeforces.com/contest/1148/problem/F (6) //[VERY NICE][INDUCTION][CONSTRUCTIVE]

https://devskill.com/CodingProblems/ViewProblem/566 (2)

https://codeforces.com/gym/102006/problem/F (6) //[VERY NICE][DP]

http://codeforces.com/gym/101908/problem/I (3) //[EASY][XOR]

http://codeforces.com/contest/879/problem/C (3) //[NICE] one of each operation is enough

http://codeforces.com/contest/92/problem/B (2) //Bit addition/shifting (but big number)

http://codeforces.com/contest/907/problem/C (3) //Nice but ugly statement: sets

11659 UVA (4)

11535 UVA (4)

http://codeforces.com/contest/779/problem/E (5) //NICE + Parsing

http://www.spoj.com/problems/EC_CONB/ (1) //reverse numbers

http://codeforces.com/contest/769/problem/D (4) //freq + brute-force

http://www.spoj.com/problems/HAP01/ (2) //builtin_popcount

http://codeforces.com/contest/862/problem/C (3) //VERY NICE &mdash; Random works well

http://www.spoj.com/problems/KOMPICI/ (4) //NICE &mdash; Bitmask over digits

</spoiler>

<spoiler summary="bitset">

http://www.spoj.com/problems/ADACOINS/

http://www.spoj.com/problems/ADACHERY/

http://www.spoj.com/problems/ADAFUROW/

https://codeforces.com/contest/1194/problem/E (5) //[NICE][BRUTE]

https://www.spoj.com/problems/TTRGRAPH/ (4) //[NICE][GRAPH][CLIQUES]

https://www.spoj.com/problems/ILD18ACP/ (5) //[NICE][GRAPH][PATH]

http://codeforces.com/contest/914/problem/F (7) //[VERY NICE][POLYMUL-LIKE][BRUTE]

http://codeforces.com/contest/117/problem/C (5) //Finding 3cycles in directed graph [NICE]

http://codeforces.com/contest/754/problem/E 6

http://www.spoj.com/problems/UCBINTC/ 5 //polymul with bitset

http://codeforces.com/contest/33/problem/D (4) //VERY NICE [LCA works too]

http://codeforces.com/contest/918/problem/C (4) //Brute-force+Bitset (or...)

</spoiler>

<spoiler summary="bridges">

http://codeforces.com/contest/118/problem/E (4) //[NICE]//Orientation [+DFS]

315 &mdash; Network

796 &mdash; Critical Links

UVA	12363

Gym	100114J [2012-2013 ACM-ICPC, NEERC, Central Subregional Contest]

http://www.spoj.com/problems/ONBRIDGE/ [ONLINE][HARD][NICE][D&C]

http://codeforces.com/contest/732/problem/F 7

http://codeforces.com/contest/700/problem/C 7

http://www.spoj.com/problems/EC_P/ (3) //bridges ONLY

http://www.spoj.com/problems/SUBMERGE/ (3) //Direct articulation

http://www.spoj.com/problems/GRAFFDEF/ (5) //Bridge tree

http://codeforces.com/contest/1000/problem/E // Sugested by [user:Muhanad_Alwarareh]


</spoiler>

<spoiler summary="brute-force">

https://codeforces.com/gym/102302/problem/A (4) //[RMQ][BS][NEXT]

https://codeforces.com/contest/1166/problem/D (4) //[NICE][OBSERVATION][SEQUENCE][COMPLEXITY]

https://codeforces.com/contest/1169/problem/D (4) //[NICE][PROOF]

https://codeforces.com/contest/1169/problem/B (3) //[VERY NICE][FREQUENCY]

https://www.spoj.com/problems/YOSEQ/ (3) //[NICE][OBSERVATION]

UVA 13296 (5) //[NICE][RECURSION]

http://codeforces.com/gym/100112 (7) [L] //[PRECISION]

http://codeforces.com/gym/101806/problem/X (6) //[VERY NICE][DFS][IFS][OBSERVATION]

8259 - High Score [LA] (4) //[VERY NICE][TS works too] add only low number to minimum (NOT WORKING?)

http://codeforces.com/contest/922/problem/B (2) //Test all pairs - observe 3rd

http://codeforces.com/contest/919/problem/B (1) //Simply simulate

http://codeforces.com/contest/146/problem/B (2) //Test all bigger numbers

http://codeforces.com/contest/911/problem/B (1)

7692 - Square Deal (4) //Permutations+Swap

http://codeforces.com/contest/907/problem/A (2) //try all triples 0→ 200

http://codeforces.com/contest/124/problem/B (3) //next-permutation

http://codeforces.com/contest/910/problem/C (3) //Next-permutation

http://codeforces.com/contest/898/problem/B (2) //Try all possibilities

6160 - Countdown (5) //[NICE][DFS][EFFICIENT?]

http://codeforces.com/contest/122/problem/C (3) //Just around 2^10 lucky [RECURSION]

7899 - Mr. Panda and Strips (4) //Weak test-cases

7671	What a Beautiful Lake (2) //Try up/down from every node

http://codeforces.com/contest/110/problem/A (1) //4 or 7

http://codeforces.com/contest/106/problem/B (2) //Cycles -_-

http://codeforces.com/contest/895/problem/A (2) //All segments [in circle]

http://codeforces.com/contest/893/problem/B (2) //Try each divisor

http://codeforces.com/contest/894/problem/A (1) //3-cycles

http://codeforces.com/contest/892/problem/C (3) //Try to find "1" ASAP

http://codeforces.com/contest/102/problem/A (2) //Iterate over all triples

http://codeforces.com/contest/96/problem/B (2) //Check all

http://codeforces.com/contest/94/problem/B (1) //3cycles

http://codeforces.com/contest/887/problem/B (3) //Test all numbers

http://codeforces.com/gym/101597/problem/A (4) //[MATH][MODULO][SIMULATION]

http://codeforces.com/contest/68/problem/C (5) //[VERY NICE][RECURSION][MAX COST MIN FLOW]

http://codeforces.com/contest/68/problem/A (1) //Simple simulation

http://codeforces.com/contest/66/problem/B (2) //Test always whole platform

http://codeforces.com/contest/879/problem/C (3) //[NICE] one of each operation is enough

http://codeforces.com/contest/46/problem/C (2) //[2pointers][N^2 works too]

http://codeforces.com/contest/47/problem/D (4) //[Implementation][DFS]

http://codeforces.com/contest/51/problem/D (4) //Check all/check without 1s/2nd

http://code-festival-2017-qualc.contest.atcoder.jp/tasks/code_festival_2017_qualc_b (2)

http://codeforces.com/contest/53/problem/B (3) //at most 60 possibilities

http://codeforces.com/contest/55/problem/B (3) //Try all permutations & possibilities [NICE]

http://codeforces.com/contest/877/problem/B (3) //NICE [N^2][PrefixSum]

LA 6623 - Battle for Silver (3) //4 for-cycles inside ~ K4 search

UVA 12169 (2)

http://codeforces.com/contest/725/problem/C 4

http://codeforces.com/contest/725/problem/E 6

http://codeforces.com/contest/724/problem/B 3

11961 UVA (2)

11898 UVA (4)

11659 UVA (4)

http://codeforces.com/contest/753/problem/C 7

11699 UVA (4)

11548 UVA (3)

11471 UVA (5) //With dynamic programming

http://codeforces.com/contest/698/problem/D 8 //with geometry

http://codeforces.com/gym/101840 [F] (5) //[NICE][BS][DISTANCE]

11206 UVA (6) //4^20 (but somehow passes)

11214 UVA (6) //Úvaha + pruning

11127 UVA (4) //Simple dfs [just realize you can do so]

http://www.spoj.com/problems/BOKAM143SOU/ (3) //just implement for-cycles

http://www.spoj.com/problems/BLOPER/ (4) dfs with little pruning

13173 UVA (3) //just brute-force + branching

http://codeforces.com/contest/799/problem/D (4) //VERY NICE [only top 34 needed] &mdash; trick with 2 [~20]

10890 UVA (4) //Simple brute-force times out, but with simple pruning AC (answer detection

http://codeforces.com/contest/813/problem/B (3) //All*All (BF) care for overflow! NICE & EASY

http://codeforces.com/contest/817/problem/C (3) //Check S+Constant (NICE!)

10732 UVA (2) //Brute-force passes .. just don't trust them O(N^2)

10748 UVA (5) //VERY Nice (knights have K^2 moves not 8^K)

http://codeforces.com/contest/818/problem/D (4) //NICE for each 'A' check all remaining (max SQRT)

http://codeforces.com/contest/834/problem/E (5) //NICE &mdash; hard to imple: all 11122...999 OK

http://www.spoj.com/problems/JHAGIRLS/ (4) //Efficient &mdash; or store output in array

http://codeforces.com/contest/846/problem/B (3) //Brute-force

http://www.spoj.com/problems/ALONE/ (4) //Generate everything <10^15 [NICE]

http://codeforces.com/contest/861/problem/B (3) //Check all floor-sizes

http://www.spoj.com/problems/RRANGE/ (3) //Compare all queries agains all updates + GAUSS

http://codeforces.com/contest/598/problem/B (3) //Treap works too ;-)

http://www.spoj.com/problems/AMR10I/ (4) //Can be solved with brute-force with dp

http://codeforces.com/contest/868/problem/C (4) //Brute-force (fixet at most 6 each bits)

http://codeforces.com/contest/868/problem/D (5) //NICE: Maximal K is low (I assumed 15)

http://codeforces.com/contest/31/problem/C (2) //LOW-Constaints: N^2

http://codeforces.com/contest/32/problem/D (3) //Simply try all possibilities

http://codeforces.com/contest/876/problem/C (3) //Try N and ~100 lower

http://codeforces.com/contest/44/problem/B (2) //N^2 works fine

</spoiler>

<spoiler summary="centroid">

https://codeforces.com/gym/101991/problem/A (5) //[VERY NICE][FW]

http://codeforces.com/gym/101864 [D] (5) //[NICE][SACK][ARPA][HLD]

http://codeforces.com/gym/101840 [E] (5) //NICE

DCP-176: Motku2 [DevSkills]

http://codeforces.com/contest/715/problem/C 9

http://codeforces.com/contest/741/problem/D 8

13164 UVA (7)

http://codeforces.com/contest/752/problem/F 5

http://codeforces.com/contest/766/problem/E 6

http://codeforces.com/contest/833/problem/D 7 //Very nice &mdash; hard (thinking + imple) + FW

http://www.spoj.com/problems/HOLI/ (4) //VERY NICE: 2*Distances from centroids

</spoiler>

<spoiler summary="coloring">

https://codeforces.com/gym/102006/problem/K (6) //[VERY NICE][THEOREM][OBSERVATION]

http://codeforces.com/contest/741/problem/C 6

11331 UVA (4)

http://codeforces.com/contest/664/problem/D 4

</spoiler>

<spoiler summary="combinatorics">

http://www.spoj.com/problems/ADATEAMS/

http://www.spoj.com/problems/ADASUM/

https://codeforces.com/contest/1166/problem/A (2) //[B2]

https://codeforces.com/contest/1207/problem/D (4) //[NICE][FACTORIAL][STL]

https://codeforces.com/contest/1204/problem/E (6) //[COMBINATION NUMBERS]

https://codeforces.com/contest/1173/problem/D (4) //[VERY NICE][DFS][FACTORIAL]

https://atcoder.jp/contests/abc136/tasks/abc136_f (5) //[VERY NICE][IE][POWER][FENWICK]

https://codeforces.com/contest/1178/problem/C (3) //[NICE][EASY][POWER]

https://codeforces.com/gym/101972/problem/J (4) //[NICE][THEOREM][COMB-NUMBERS]

https://codeforces.com/gym/101972/problem/I (5) //[NICE][SHORT][COMB-NUMBERS]

http://codeforces.com/gym/101628/problem/G (5) //[NICE][COMB-NUMBERS]

http://codeforces.com/gym/101864 [E] (3) //Combination number, power

http://codeforces.com/gym/101879/problem/E (2) //Power of 2

http://codeforces.com/gym/101873 (5) //Necklace (mby burnside)

http://codeforces.com/gym/101808/problem/F (3) //[EASY]][FACTORIAL]

http://codeforces.com/problemset/problem/364/A (4) //[NICE][STL-or-sorting][IF]

http://codeforces.com/contest/145/problem/D (7) //[VERY NICE][SET][OBSERVATION][BS][BIG]

http://codeforces.com/contest/909/problem/B (3)

http://codeforces.com/contest/131/problem/C (3) //[EASY][BRUTE-FORCE][COMB-NUMBERS]

http://codeforces.com/contest/131/problem/B (2) //[EASY]

http://codeforces.com/contest/129/problem/E (5) //[NICE][COMB-NUMBERS]//Observe

http://codeforces.com/contest/111/problem/D (5) //[COMB-NUMBERS][POWER][VERY NICE][DP]

http://codeforces.com/contest/895/problem/D (4) //[COMB-NUMBERS][OPTI]

http://codeforces.com/contest/893/problem/E (5) //[COMB-NUMBERS][NUMBER-THEORY]

http://codeforces.com/contest/894/problem/B (3) //try without last row

http://codeforces.com/contest/890/problem/E (6) //Permutations

http://codeforces.com/contest/52/problem/B (4) //[NICE][PREPROCESS][ROTATION]

3917 //Grid tiling [fancy approximation fomula]

http://codeforces.com/contest/760/problem/F

https://devskill.com/CodingProblems/ViewProblem/61

https://devskill.com/CodingProblems/ViewProblem/255

UVA	10918

UVA	12576

UVA	1118 //Parity

http://www.spoj.com/problems/HLP_RAMS/ //Comb parity

Project Euler #78: Coin partitions //Partition function

http://www.spoj.com/problems/MAIN75/ //DP #of trees

12001 UVA (3)

12034 UVA (4)

11719 UVA (5)

11798 UVA (5)

11282 UVA (4) //dearrangement

11174 UVA (4)

http://codeforces.com/contest/666/problem/C 7

http://www.spoj.com/problems/JOKER1/ 3 prod(Ai-i)

http://www.spoj.com/problems/ANTP/ //4

http://codeforces.com/contest/645/problem/E (5) //formula: A[i]=Sum(A)+1

http://www.spoj.com/problems/SPCE/ (5) // N^{K-2}*Prod(comp_size)

http://codeforces.com/contest/785/problem/D (5) // F'(' C"(+)-1","("

13184 UVA (3)

http://codeforces.com/contest/816/problem/D (5) // Observation

13214 (4) //OEIS? : C(N+M-2,N-1)

http://codeforces.com/contest/844/problem/B (2) //Easy &mdash; pro prvaky

http://www.spoj.com/problems/JOSWAP/ (3) //Frequence array

http://www.spoj.com/problems/UCV2013E/ (4) //NICE&EASY: Choose steps to direction

http://www.spoj.com/problems/PARCARD1/ (4) //Partition function (raw)

http://www.spoj.com/problems/GOODB/ (2) //Easy (NICE): Choose [order]

http://www.spoj.com/problems/LOOPEXP/ (4) //A000254/N!

http://www.spoj.com/problems/DTPOLY/ (5) //DP might work too

http://www.spoj.com/problems/DTPOLY2/ (7) //Harder version of above (NICE but hell)

http://www.spoj.com/problems/HC12/ (3) //NICE &mdash; Sort + C(i,K-1)*A[i]

http://www.spoj.com/problems/STONE2/ (4) //NICE &mdash; Mostly DP [INVERSION][FACTORIAL]

http://www.spoj.com/problems/MAIN8_D/ (5) //NICE &mdash; Suffixes/Prefixes (same add 2^i)

http://www.spoj.com/problems/ITRIX_E/ (4) //VERY NICE &mdash; #Nonattacking 2-queens

http://www.spoj.com/problems/MAXSUB/ (3) //NICE &mdash; Subsets made of zeroes

http://www.spoj.com/problems/SKYLINE/ (3) //Catalan numbers [weird modulo &mdash; care]

http://codeforces.com/contest/26/problem/D (5) //Division of two combintion numbers [NI:/]

http://codeforces.com/contest/872/problem/E (6) // Prod:Sum(C(DistLines,CompSize))

</spoiler>

<spoiler summary="constructive">

https://codeforces.com/contest/1208/problem/C (4) //[NICE][SEQUENCE][XOR][D&C]

https://codeforces.com/contest/1166/problem/B (3) //[NICE][STRINGS][DIVISORS]

https://codeforces.com/contest/1206/problem/F (6) //[NICE][OBSERVATION][DFS][CENTROID]

https://codeforces.com/contest/1206/problem/C (3) //[NICE]

https://codeforces.com/contest/1148/problem/C (4) //[SORTING][PAPERWORK]

https://codeforces.com/contest/1174/problem/D (4) //[OBSERVATION][PREFIX SUM][SIMPLE CODING]

https://codeforces.com/contest/1174/problem/C (4) //[VERY NICE][SIEVE]

https://codeforces.com/contest/1173/problem/B (3) //[VERY NICE][MATH]

https://codeforces.com/contest/1202/problem/D (4) //[NICE][MATH][GREEDY]

https://codeforces.com/contest/1199/problem/E (5) //[VERY NICE!][OBSERVATION][DFS]

https://codeforces.com/contest/1180/problem/D (5) //[VERY NICE][OVSERVATION]

https://codeforces.com/contest/1178/problem/D (4) //[VERY NICE][OBSERVATION][NUMBER THEORY]

https://codeforces.com/contest/1187/problem/C (4) //[NICE][IMPLEMENTATION]

http://codeforces.com/contest/922/problem/F (6) //[NICE][MATH][GREEDY]

http://codeforces.com/contest/916/problem/C (3) //Graph construction

http://codeforces.com/contest/148/problem/B (3) //[SIMULATION](math or bs)

http://codeforces.com/contest/909/problem/F (6) //[VERY NICE][BITS]

http://codeforces.com/contest/141/problem/C (4) //[NICE][BRUTE-FORCE]

http://codeforces.com/contest/907/problem/D (5) //[VERY NICE][RANDOM]

http://codeforces.com/contest/124/problem/C (3) //[NICE][SIEVE]

http://codeforces.com/contest/125/problem/C (4) //[NICE][C(N,2)]

http://codeforces.com/contest/902/problem/C (4) //[NICE]//Tree isomorphism

http://codeforces.com/contest/112/problem/C (3) //[GREEDY]//Max + 1s

http://codeforces.com/contest/110/problem/B (2) //Easy modulo

http://codeforces.com/contest/894/problem/C (3) //[VERY NICE] //AiAiGCD

http://codeforces.com/contest/97/problem/B (4) //NICE - Walls in middles [D&C]

http://codeforces.com/contest/85/problem/A (3) //MODULO / SHIFT

http://codeforces.com/contest/81/problem/D (3) //NICE - MAX(N/2) - even/odd

http://codeforces.com/contest/63/problem/D (3) //NICE[GO BY LINES][4 WAYS B/D ODD/EVEN]

http://codeforces.com/contest/42/problem/C (4) //Constructive works too but random is fine :)

http://codeforces.com/contest/43/problem/D (3) //NICE - Easy to see [implementation]

http://codeforces.com/contest/53/problem/C (2) //EASY [B/E Alternate]

http://codeforces.com/contest/877/problem/C (3) //NICE 3*Alternative

http://codeforces.com/contest/802/problem/H (6) //We can do "N+k" by adding a letter p+k*x+u+xx

http://codeforces.com/contest/12/problem/E (5) //g[i][j]=1+(i+j)%(N-1) [+/-]

http://codeforces.com/contest/22/problem/C (4) //Start and then clique without v (+ random)

http://codeforces.com/contest/26/problem/C (5) //make Even*Even: do by 2*2 fields

http://codeforces.com/contest/41/problem/E (4) //[NICE][CN/2,N/2]

http://codeforces.com/contest/78/problem/B (2) //NICE - last 3 and then rest in modulo

http://codeforces.com/contest/109/problem/D (5) //[NICE][BACK-POINTERS][SIMULATION][SORT]

</spoiler>

<spoiler summary="dfs">

http://www.spoj.com/problems/ADASEA/

https://codeforces.com/contest/1176/problem/E (4) //[NICE][CONSTRUCTIVE][TREE][TOPO]

https://codeforces.com/contest/1186/problem/F (5) //[NICE][GREEDY][CONSTRUCTIVE]

https://codeforces.com/contest/1189/problem/D2 (5) //[NICE][CONSTRUCTIVE]

https://atcoder.jp/contests/agc035/tasks/agc035_b (4) //[NICE][DIRECTION]

https://www.spoj.com/problems/CHUNK2/ (3) //[DFS][PRIMES]

https://codeforces.com/gym/101981 [K] (4) //[VERY NICE][IMPLE][TREE][SIMULATION]

https://www.urionlinejudge.com.br/judge/en/problems/view/1621 (4) //[TREE][IMPLE]

https://www.urionlinejudge.com.br/judge/en/problems/view/1610 (3) //[CYCLE]

https://www.urionlinejudge.com.br/judge/en/problems/view/2911 (4) //[NICE][RULES][SIMPLE]

https://codeforces.com/gym/102001/problem/K (4) //[VERY NICE]

https://codeforces.com/gym/101972/problem/B (6) //[VERY NICE][TREE][STL]

https://toph.co/p/incompatible-crops (2)

http://codeforces.com/gym/100112 [K] (5) //[NICE][BS][COLORING]

http://codeforces.com/gym/101962 [D] (6) //[NICE] //Bitset shall work too

4286 - Equilibrium Mobile [LA] (5) //[VERY NICE][OBSERVATION][TREE][DP]

http://codeforces.com/gym/101801 (4) [H] //[TREE][DP] //More dfss

https://www.urionlinejudge.com.br/judge/en/problems/view/2732 (3) //Easy flood

http://codeforces.com/contest/920/problem/E (5) //[NICE][DFS][SET] //Or clever random

http://codeforces.com/contest/915/problem/D (4) //[VERY NICE][CYCLES DETECTION (ORIENTED)]

http://www.spoj.com/problems/CTTC/ (3) //[EASY][GRAPH-RECONSTRUCTION]

7951 - Islands (3) //[NICE]Flood-Fill

http://codeforces.com/contest/901/problem/D (7) //Observations / Tree reduction

http://codeforces.com/contest/902/problem/B (3) //No dfs needed

http://codeforces.com/gym/101630 {C}(4) //[NICE][SCC]

http://codeforces.com/gym/101620 {J}(4) //DFS + multiples of divisors

http://codeforces.com/contest/120/problem/F (3) //Width of tree

7606 - Percolation (3) //Dfs on grid [EASY]

http://codeforces.com/contest/116/problem/C (2) //[DEPTH]

8080 - Christmas Tree (3) //[SIMPLE][NICE]

6584 - Escape (8) //[VERY VERY VERY NICE][COMPRESSION][MERGING] //Hard but I recommend this one!!

6590 Digraphs (4) //[VERY NICE][CYCLES][DP][IDEA]

http://codeforces.com/contest/893/problem/C (3) //Minimum from each connected component

http://codeforces.com/contest/884/problem/C (3) //[EASY][PERMUTATIONS][SORTING]

http://codeforces.com/contest/883/problem/G (4) //Greedy picking

http://codeforces.com/contest/60/problem/B (3) //3D Flood-Fill [NICE][EASY]

http://codeforces.com/contest/60/problem/C (4) //[VERY NICE][BF]//Not many real possibilities

https://devskill.com/CodingProblems/ViewProblem/3

https://devskill.com/CodingProblems/ViewProblem/17

https://devskill.com/CodingProblems/ViewProblem/118 //Kind-of

657 &mdash; The die is cast [UVA]

12186 UVA (3)

http://codeforces.com/contest/734/problem/E (5)

http://codeforces.com/contest/727/problem/A (3)

http://codeforces.com/contest/723/problem/E (6)

http://codeforces.com/contest/709/problem/E (6)

http://codeforces.com/contest/710/problem/E (4)

http://codeforces.com/contest/758/problem/E (8)

11323 UVA (5)

http://codeforces.com/contest/760/problem/B (3)

http://codeforces.com/contest/761/problem/E (6)

http://codeforces.com/contest/638/problem/B (3) //connect cons. letters

http://codeforces.com/contest/638/problem/C (4) //greedy idea &mdash; easy

http://codeforces.com/contest/638/problem/D (5) //spec-DAG articulatin

http://codeforces.com/contest/767/problem/C (4)

http://codeforces.com/contest/781/problem/C (5)

http://codeforces.com/contest/794/problem/D (5) //NICE! Right done dfs

http://codeforces.com/contest/802/problem/K (5) //Slightly DP-like (NICE) TREE

http://codeforces.com/contest/813/problem/C (3) //Simply 2 DFS: NICE + EASY

http://codeforces.com/contest/841/problem/D (4) //DFS while tracking "next"

http://codeforces.com/contest/845/problem/G (5) //Keep track of cycles

http://codeforces.com/contest/844/problem/E (5) //Post-Order → line, Connect i → N-2: star

http://www.spoj.com/problems/CAC/ (5) //VERY NICE! &mdash; Find all cycles in cactus

http://codeforces.com/contest/849/problem/C (3) //State search by gauss

http://codeforces.com/contest/846/problem/E (5) //NICE: DFS + some overflow logic

http://www.spoj.com/problems/KOZE/ (3) //NICE: Floods

http://www.spoj.com/problems/RIOI_2_3/ (4) //DFS /OR/ BFS /OR/ DSU [NICE][EASY][BF]

http://www.spoj.com/problems/MAKEMAZE/ (3) //EASY &mdash; Simple dfs on grid

http://codeforces.com/contest/861/problem/F (5) //VERY NICE: Modify dfs tree so it remains connected

http://www.spoj.com/problems/GHOSTS/ (3) //NICE &mdash; must remain dag after each QR

http://www.spoj.com/problems/AMR10J/ (5) //VERY NICE! &mdash; DFS+DP [DAG with cycles]

http://codeforces.com/contest/24/problem/A (2)//NICE [DFS-ON-CYCLE]

http://codeforces.com/contest/29/problem/C (3) //Find begining/end of line (graph)

http://codeforces.com/contest/29/problem/D (4) //Tree [implementation][simulation]

</spoiler>

<spoiler summary="digits">

https://devskill.com/CodingProblems/ViewProblem/564 (2) //[OBSERVATION]

http://www.spoj.com/problems/PR003004/ (4) //Simple digits count

http://codeforces.com/contest/770/problem/B (3) //max num max digsum

</spoiler>

<spoiler summary="dijkstra">

http://www.spoj.com/problems/ADATRIP/

https://www.urionlinejudge.com.br/judge/en/problems/view/1655 (4) //[EASY][PROBABILITY]

https://www.urionlinejudge.com.br/judge/en/problems/view/2910 (4) //[TREE]

http://codeforces.com/gym/101628/problem/f (4)

http://codeforces.com/gym/100112 [E] (6) //[NICE][BS][GEOMETRY]

http://codeforces.com/gym/101845/problem/J (5) //[NICE][OBSERVATION][TWICE]

http://codeforces.com/gym/101801 [K] (5) //[NICE][MULTIPLE NODES]

http://codeforces.com/gym/101879/problem/F (8) //[NICE][BRIDGE]

http://codeforces.com/gym/101666 [D] (4) //[NICE]

http://codeforces.com/contest/144/problem/D (4) //[VERY NICE][IFS]

http://www.spoj.com/problems/ADRABR/ (3) //Classical dijkstra - bad statement

http://codeforces.com/contest/141/problem/D (5) //[NICE]Many Conditions

6583 Subway (5) //[NICE]//Not exactly dijkstra by slightly similar [IMPLEMENTATION]

3850 [LA]

Gym	100625D [2013 Benelux Algorithm Programming Contest (BAPC 13)]

UVA	12950

Gym	100753A [2015 German Collegiate Programming Contest (GCPC 15) + POI 10-T3]

UVA	13030

UVA	1027

UVA	11377

http://codeforces.com/problemset/problem/843/D

11813 UVA

Gym	101242B [2016 ACM-ICPC World Finals] //+DP

Gym	100923B [2015 ACM National Contest Romania &mdash; Round 1]

UVA	11833

http://www.spoj.com/problems/EZDIJKST/en/

LightOJ	1019

UVA	13010 //+TS

2819 [LA]

UVA	12144

http://codeforces.com/contest/716/problem/D 7

12047 UVA 4

11514 UVA 4

http://codeforces.com/contest/757/problem/F 7

11338 UVA (4)

11374 UVA (4)

11097 UVA (4) //Divide to N*1000 nodes and go!

13172 UVA (5) //6*DJ per query + permutations

10816 UVA (4) //Easy Linear-Search by answer + DJ with path

http://codeforces.com/contest/827/problem/F 7 //Very nice &mdash; Even&Odd

http://www.spoj.com/problems/DELIVER/ (5) //Normalize coordinates + Optimalize

http://www.spoj.com/problems/CCHESS/ (4) //Dijkstra as knight

</spoiler>

<spoiler summary="divide_conquer">

https://codeforces.com/contest/1175/problem/F (7) //[VERY NICE][HASH][RANDOMISATION]

https://codeforces.com/contest/1181/problem/E2 (7) //[VERY NICE][SORTING][ST]

https://codeforces.com/contest/1181/problem/E1 (5) //[VERY NICE][OBSERVATION][SORTING]

https://codeforces.com/gym/102058/problem/G (7) //[VERY NICE][BS][PRIORITY_Q]

http://codeforces.com/gym/101845/problem/L (6) //[VERY NICE][INDUCTION]

http://codeforces.com/gym/101801 [J] (5) //[NICE][TRIE][RMQ]

8257 - Factor-Free Tree [LA] (6) //[VERY VERY NICE][PRIMES][FACTOR]

https://www.urionlinejudge.com.br/judge/en/problems/view/1683 (4) //RAW histogram

http://codeforces.com/contest/817/problem/D (5) //Very nice NlogN

http://www.spoj.com/problems/DYNACON2/ (8) //Lesser hell &mdash; offline Nlog(N) /or/ NlogN^2

http://codeforces.com/contest/876/problem/F (5) //VERY NICE &mdash; Find greatest + next/back functions

</spoiler>

<spoiler summary="divisors">

https://codeforces.com/gym/102302/problem/B (4) //[FACTORISATION][NUMBER THEORY]

https://codeforces.com/contest/1176/problem/D (4) //[NICE][GREEDY][SORTING]

https://atcoder.jp/contests/abc136/tasks/abc136_e (5) //[NICE][GREEDY][DIVISORS]

https://codeforces.com/contest/1183/problem/F (5) //[VERY NICE][SORTING][OBSERVATION][BF]

https://www.spoj.com/problems/KPOWERSUM/ (4) //[FACTORISATION]

http://codeforces.com/gym/101992/problem/D (5) //[VERY NICE][IE][NUMBER THEORY]

http://codeforces.com/gym/101982 [B] (5) //[FACTORISATION][GCD][SIEVE]

http://codeforces.com/gym/101864 [G] (5) //[VERY NICE][FACTORISATION][GCD]

http://codeforces.com/gym/101840 [D] (4) //[EVENTS][NICE]

http://codeforces.com/gym/101741/problem/F (6) //[NICE][PROBABILITY][GCD]

http://www.spoj.com/problems/FRNDAM/ (3) //Simply find sum of all divisors (low constraints)

http://codeforces.com/contest/920/problem/F (5) //[NICE][FAST FALL][SET][DIVISORS]

7726	A Simple Math Problem (4) //TLE if naive (consider only divisors)

http://codeforces.com/contest/112/problem/D (4) //[NICE] Last-position [FACTOR]

http://codeforces.com/contest/75/problem/C (3) //[NICE][BS]

LightOJ	1068

LightOJ	1134

Project Euler #95: Amicable chains

NAJ0001 &mdash; Divisible Number Sum [SPOJ]

http://www.spoj.com/problems/LCMSUM/

https://www.hackerrank.com/contests/101hack38/challenges/easy-gcd-1/problem

UVA	13085

http://www.spoj.com/problems/CDRSANJ/

http://www.spoj.com/problems/DIVSEQ/

UVA	12154

UVA	13058

http://www.spoj.com/problems/EC_DIVS/

https://www.codechef.com/problems/CHEFKEY

http://codeforces.com/problemset/problem/671/C

Gym	101411G	 [2009-2010 ACM-ICPC, NEERC, Western Subregional Contest]

http://codeforces.com/problemset/problem/831/F

http://codeforces.com/problemset/problem/839/D

12934 &mdash; Factorial Division [UVA]

UVA	10880

http://www.spoj.com/problems/PSTR/

http://codeforces.com/problemset/problem/27/E

[LA] 3014

UVA	12843

https://www.urionlinejudge.com.br/judge/en/problems/view/1164

http://codeforces.com/problemset/problem/803/F

10892 &mdash; LCM Cardinality

http://www.spoj.com/problems/GCDEX/

http://www.spoj.com/problems/INVDIV/

13083 &mdash; Yet another GCDSUM //ll

http://www.spoj.com/problems/IITKWPCF/ //ll

UVA	13185

UVA	13194

UVA	11388

http://www.spoj.com/problems/SAS002/

12425 &mdash; Best Friend

http://codeforces.com/problemset/problem/703/E

https://www.hackerearth.com/problem/algorithm/harry-gets-into-infy/

UVA	10830 //SUM

http://www.spoj.com/problems/DIVSUM/en/ //SUM

http://www.spoj.com/problems/AFS/ //SUM

UVA	11526 //SUM

</spoiler>

<spoiler summary="dp">

http://www.spoj.com/problems/ADAZOO/

http://www.spoj.com/problems/ADASEQEN/

http://www.spoj.com/problems/ADAMOLD/

http://www.spoj.com/problems/ADASALE/

https://codeforces.com/gym/102302/problem/E

https://codeforces.com/gym/102307/problem/G (4) //[DAG][PRIORITY][GREEDY]

https://codeforces.com/contest/1208/problem/F (6) //[VERY NICE][BITS][GREEDY][SOS]

https://codeforces.com/contest/1174/problem/E (6) //[VERY NICE][NUMBER THEORY][OBSERVATION]

https://codeforces.com/contest/1203/problem/F2 (6) //[VERY NICE][GREEDY][SORTING][CASES]

https://codeforces.com/contest/1176/problem/F (5) //[NICE][IMPLE][SORTING]

https://codeforces.com/contest/1200/problem/F (6) //[NICE][DFS][GRAPH][LCM][MATH]

https://codeforces.com/contest/1201/problem/D (5) //[NICE][DP][IMPLE][CASES]

https://www.spoj.com/problems/THECODE/ (4) //[BITMASK]

https://codeforces.com/contest/1199/problem/F (5) //[NICE][DIMENSIONS]

https://codeforces.com/contest/1183/problem/H (4) //[NICE][SUBSEQUENCE][NEXT]

https://codeforces.com/contest/1183/problem/E (4) //[NICE][SUBSEQUENCE][NEXT]

https://codeforces.com/contest/1178/problem/F2 (7) //[VERY NICE][OBSERVATION]

https://codeforces.com/contest/1178/problem/F1 (5) //[NICE][MATH][REDUCTION]

https://codeforces.com/contest/1178/problem/B (3) //[EASY]Not even real DP

https://codeforces.com/contest/1195/problem/C (3) //[EASY]

https://codeforces.com/contest/1189/problem/F (6) //[VERY NICE][OBSERVATION]

https://atcoder.jp/contests/agc035/tasks/agc035_d (5) //[VERY NICE][BIT][IDEA]

https://www.spoj.com/problems/PLOVER/ (4) //[NICE][DIGITS]

https://www.spoj.com/problems/NICESEQ/ (4) //[DIGITS][POSSIBLY FASTER]

https://codeforces.com/gym/101981 [L] (5) //[NICE]

https://www.spoj.com/problems/RANDMOD/ (4) //[OBSERVATION][SEQUENCE]

https://www.urionlinejudge.com.br/judge/en/problems/view/1592 (4) //[GRAPH]

https://www.urionlinejudge.com.br/judge/en/problems/view/2824 (4) //Classical

https://codeforces.com/gym/102006/problem/D (4) //[NICE][OBSERVATION]

https://codeforces.com/gym/102021 [K] (4)

https://codeforces.com/gym/102058/problem/D (5) //[NICE][DOMINATION]

UVA 13294 (4) //[BIT]

http://codeforces.com/gym/101992/problem/A (6) //[BITS][OBSERVATION]

http://codeforces.com/gym/101628/problem/H (3) //[NICE][CLASSICAL][DAG]

http://codeforces.com/gym/101628/problem/A (3)

http://codeforces.com/gym/100112 [J] (4) //[NICE][TREE]

http://codeforces.com/gym/101982 [D] (5) //[VERY NICE][BITS] //Window

http://codeforces.com/gym/101982 [C] (4) //Classical combinatorics

http://codeforces.com/gym/101845/problem/E (5)

https://www.codechef.com/problems/SPECTAC (5) //[NICE]

http://codeforces.com/gym/101801 [E]

http://codeforces.com/gym/101801 [D] (6) //[VERY NICE][SEGMENT TREE][SORTING][NORMALIZE]

http://codeforces.com/gym/101873 [J] (7) //[NICE][IMPLEMENTATION][STRING][SUBSUBSET]

http://codeforces.com/gym/101889 [E] (4)

http://codeforces.com/gym/101808/problem/D (7) //[NICE][OPTIMISATION][EFFICIENCY]

http://codeforces.com/gym/101666 [I] (4)

http://codeforces.com/gym/101840 [A] (4) //Doubles

DevSkills 475: Bunty's Xor Game (4) //[BITS][GAME THEORY]

https://www.devskill.com/CodingProblems/ViewProblem/489 (5) //[NICE][FACTORISATION]

DevSkills 534 (4) //[BITSET][COMBINATIONS]

http://codeforces.com/gym/101650 [D] (5) //Not hard - more coding + printing

13286 - Ingredients (4) //[NICE][DAG] Classical

8299 - Bricks (5) //[NICE][COMBINATORICS][SORTING]

http://codeforces.com/contest/934/my (4) //Subsequence

http://codeforces.com/contest/922/problem/E (5) //find max mana

http://codeforces.com/contest/920/problem/D (4) //[NICE][KNAPSACK-MODULO][GREEDY]

http://codeforces.com/contest/919/problem/D (4) //[NICE][DFS][CYCLE][DAG]

http://codeforces.com/contest/914/problem/C (3) //[DIGITS][BINARY]

http://codeforces.com/contest/913/problem/E (5) //[NICE][EXPRESSION]

http://codeforces.com/contest/148/problem/E (5) //[DP][PREFIX SUM][GREED]

http://www.spoj.com/problems/PALMKR/ (4) //Classical palindrome + print + lexicography

http://codeforces.com/contest/146/problem/E (5) //[NICE][COMBINATORICS][OBSERVATION]

http://codeforces.com/contest/909/problem/C (4) //[NICE][CLASSICAL][EASY]

7785 - m-ary Partitions (4) //Combinatorics

http://codeforces.com/contest/133/problem/E (4) //[IMPLEMENTATION]

http://codeforces.com/contest/126/problem/D (5) //[NICE]//Decomposet DP//Own hash-map

http://codeforces.com/contest/910/problem/B (3) //Or many other ways

6154	RNA Secondary Structure (5) //[NICE] Unoptimal might work too

https://arc087.contest.atcoder.jp/tasks/arc087_b (4) //[VERY NICE][OBSERVATION]

http://codeforces.com/contest/903/problem/F (5) //[VERY NICE][BITMASK][BRUTE]

http://codeforces.com/contest/903/problem/A (2) //Easy knapsack-like // Low constraints

http://codeforces.com/contest/900/problem/E (4) //[NICE]//Patter-match: FFT or KMP or Brute-Force

http://codeforces.com/contest/118/problem/D (3) //[COMBINATORICS][LOW-CONSTRAINTS]

http://codeforces.com/contest/115/problem/E (5) //[VERY NICE][SEGMENT TREE]

http://codeforces.com/contest/116/problem/D (3) //CLASSICAL[LOW-CONSTRAINTS]

10128 Queue (uva) (4) //One possibility is bitmask - second combinatorics

http://codeforces.com/contest/110/problem/C (3) //[EASY]// Greedy/math works too

8078 - Bracket Sequence (4) //[VERY NICE][DP-LINKS]

http://codeforces.com/contest/106/problem/C (3) //[NICE][EASY]

http://codeforces.com/contest/895/problem/C (4) //[NICE]

8024	Stack Construction (4) //[NICE] Palindromic style - but not exactly

7708 - Cubes (6) //[MATH]

http://codeforces.com/contest/888/problem/F (6) //[NICE][FLAG]

http://www.spoj.com/problems/ACQUIRE/ (5) //[NICE][CH-OPT]

http://codeforces.com/contest/319/problem/C (6) //[NICE][CH-OPT]

http://www.spoj.com/problems/NKLEAVES/ (5) //[NICE][DC]

http://codeforces.com/contest/76/problem/D (4) //[BITS][OVERFLOW]

http://codeforces.com/contest/73/problem/C (4) //[NICE][EASY][TRY-ALL-LETTERS]

http://codeforces.com/contest/67/problem/C (4) //[NICE][LEAVENSTEIN]

http://codeforces.com/contest/67/problem/A (3) //[EASY][PRINTING][OTHER POSSIBLE WAYS]

http://codeforces.com/contest/55/problem/D (5) //[NICE][DIGITS][EFFICIENT]

http://codeforces.com/contest/56/problem/D (4) //String modification + printing [NICE]

http://codeforces.com/contest/58/problem/E (6) //[NICE][IMPLEMENTATION]

UVA	12181

https://devskill.com/CodingProblems/ViewProblem/21

https://devskill.com/CodingProblems/ViewProblem/37

https://devskill.com/CodingProblems/ViewProblem/71

https://devskill.com/CodingProblems/ViewProblem/103

https://devskill.com/CodingProblems/ViewProblem/107

https://devskill.com/CodingProblems/ViewProblem/115

https://devskill.com/CodingProblems/ViewProblem/126

https://devskill.com/CodingProblems/ViewProblem/131

https://devskill.com/CodingProblems/ViewProblem/134

https://devskill.com/CodingProblems/ViewProblem/174

https://devskill.com/CodingProblems/ViewProblem/186

https://devskill.com/CodingProblems/ViewProblem/201

https://devskill.com/CodingProblems/ViewProblem/338

https://devskill.com/CodingProblems/ViewProblem/368

https://devskill.com/CodingProblems/ViewProblem/392

https://devskill.com/CodingProblems/ViewProblem/399

https://www.hackerrank.com/contests/world-codesprint-5/challenges/mining //Opti

UVA	12915 //Opti

UVA	12524 //Opti

http://codeforces.com/problemset/problem/631/E //CH

https://devskill.com/CodingProblems/ViewProblem/6

https://devskill.com/CodingProblems/ViewProblem/11

11552 UVA (3)

12172 UVA (3)

4507 LA (5)

4510 LA (5) [+ geometry]

12181 UVA (6)

http://codeforces.com/contest/729/problem/F 6

http://codeforces.com/contest/735/problem/E 9

http://codeforces.com/contest/731/problem/E 5

12030 UVA (4)

http://codeforces.com/contest/721/problem/E 7

http://codeforces.com/contest/742/problem/D 4

12040 UVA (5)

http://codeforces.com/contest/712/problem/D 5

13162 UVA (6)

http://codeforces.com/contest/743/problem/E 6

11908 UVA (3)

11932 UVA (4)

http://codeforces.com/contest/745/problem/E (7)

11806 UVA (4)

http://codeforces.com/contest/747/problem/F (5)

11843 UVA (4)

http://codeforces.com/contest/752/problem/E (5)

http://codeforces.com/contest/703/problem/E (7)

11753 UVA (4)

11725 UVA (5)

http://codeforces.com/contest/722/problem/E (9)

http://codeforces.com/contest/760/problem/F (8)

11795 UVA (3)

11654 UVA (4)

11523 UVA (5)

11404 UVA (4)

11432 UVA (4)

11451 UVA (4) //C==20 mistake in statement

11301 UVA (4)

http://codeforces.com/contest/762/problem/D 5

11361 UVA (4) //digit DP

11365 UVA (7)

11391 UVA (4) //easy+implementation

11394 UVA (3)

11218 UVA (2)

11125 UVA (4) //slightly implementation

11076 UVA (3)

11081 UVA (4) //3 string subsequences (beware of fail)

http://codeforces.com/contest/678/problem/E (5) //bitset dp + probability

http://codeforces.com/contest/766/problem/C (4)

http://codeforces.com/contest/667/problem/C (3)

http://www.spoj.com/problems/MOVIFAN/ (3)

http://www.spoj.com/problems/ORDSUM23/ (3)

http://www.spoj.com/problems/DIVSEQ/ (4) //N^3 (but better...) works fine

http://codeforces.com/contest/633/problem/F (7) //Tree dp

http://www.spoj.com/problems/ADJDUCKS/ (4) sort + pick 2-3 continous O(N)

http://www.spoj.com/problems/JLNT/ (4) //pick 0 or 2 | 1e3*5e3

http://www.spoj.com/problems/TPCPALIN/ (5) //500^3 works (3rd countable)

http://www.spoj.com/problems/COLORSEG/ (4) //50^4==OK 50^4log(N)=TLE NICE

http://www.spoj.com/problems/POWERCAR/ (3) //1e3*1e3*2 &mdash; follow rules

http://www.spoj.com/problems/INGRED/ (5) //TSP-like [reduce + go]

http://www.spoj.com/problems/BADXOR/ (4) //classical subsets

http://www.spoj.com/problems/SPCO/ (5) //64*64*2 DP {OPT: prime O(1) + clear only half}

http://www.spoj.com/problems/WAYHOME/ (5) //NICE: 1) 1*1 b)12,1,**,2

http://www.spoj.com/problems/NFURY/ (2) //Minimal sum of squares

http://www.spoj.com/problems/GDIL/ (3) //combinatorics

http://codeforces.com/contest/791/problem/D (5) //Tree

http://codeforces.com/contest/791/problem/E (6) //V,K,X &mdash; pick any

http://codeforces.com/contest/789/problem/C (3)

13176 (4) //N^6

13179 (5) //NICE [Ath][Bth][TimeDiff]

http://codeforces.com/contest/796/problem/E (6) //NICE: N*P*K*K (WC can't happen!)

http://codeforces.com/contest/797/problem/E (4) //NICE: Almost BF-able (but care of low K)

http://codeforces.com/contest/793/problem/D (3) //NICE & EASY: begin/end/actual/USED

http://codeforces.com/contest/803/problem/E (4) //State search &mdash; many IF's (EASY)

http://codeforces.com/contest/805/problem/F (7) //NICE: DP on tree + fast BF + hack

http://codeforces.com/contest/808/problem/E (5) //NICE!

http://codeforces.com/contest/811/problem/C (4) //Precalculate + DP (greedy thinking)

10817 UVA 4 //Easy but slightly implementation

10859 UVA 4 //Nice &mdash; on tree .. but for a reason small constrains

10898 UVA 4 //Hash is lesser than 1e6 .. try everything

http://codeforces.com/contest/812/problem/B (3) //Not only DP, yet imho easiest ..many spec cases

http://codeforces.com/contest/813/problem/D (5) //VERY VERY NICE &mdash; N*N (none picked between a/b)

http://codeforces.com/contest/814/problem/E 5 //VERY NICE &mdash; Harder imple: Combinatorics

http://codeforces.com/problemset/problem/816/E (6) //NICE &mdash; Tree (hard 2C complexity)

http://codeforces.com/contest/837/problem/D (5) //NICE &mdash; yet kinda pain [must be iterative]

http://www.spoj.com/problems/AUT/ (4) //NICE &mdash; K is interesting ~ at most 1600

http://www.spoj.com/problems/GNYR04C/ (3) //Easy &mdash; Nice idea [Big→ Low approach]

http://www.spoj.com/problems/TIEROPE/ (4) //Process 2*L ~ otherwise pick BIG

http://www.spoj.com/problems/IITKWPCE/ (4) //Palindromes [efficiency!] &mdash; NICE!

IITKWPCD SPOJ (4) //+Slightly geometry

UVA	1496 //[Steiner's Tree] Very Nice (8)

http://www.spoj.com/problems/LKS/ (3) //Classical knapsack

http://www.spoj.com/problems/UOFTAE/ (3) //Easy & Sympatic DP

http://www.spoj.com/problems/DCOWS/ (4) //Very NICE (sort + GO)

http://www.spoj.com/problems/FARIDA/ (3) //Easy & Sympatic ((u+1) | Price+(u+2))

http://www.spoj.com/problems/AU7_5/ (2) //EASY: dyn(n-1)+dyn(n-k-1)

http://www.spoj.com/problems/NAIVELOK/ (4) //NICE [depalindromisation]

http://codeforces.com/contest/846/problem/C (4) //With print

http://www.spoj.com/problems/CNT_LUCK/ (4) //Number (binary) dp [NICE] {ull care 0-1}

http://www.spoj.com/problems/MAY99_4/ (3) //Almost combinatoric Sub and 0/1,1/0

http://www.spoj.com/problems/GEEKOUNT/ (4) //Number dp

http://www.spoj.com/problems/MUTDNA/ (4) // N*2 (turned?) [not sure if grd poss.]

http://www.spoj.com/problems/RIOI_3_2/ (5) //VERY NICE (easy imple &mdash; Number Theory thinking)

http://www.spoj.com/problems/MAXWOODS/ (3) //NICE [EASY][GRID]

http://www.spoj.com/problems/DIEHARD/ (3) //Easy &mdash; prolly solvable by greedy (but dp is easier)

http://www.spoj.com/problems/DCEPC810/ (4) //VERY VERY NICE &mdash; Subsequence 2pointers+2bools

http://www.spoj.com/problems/EQ2/ (4) //NICE: Digit + Carry (from back) &mdash; iff-party

http://www.spoj.com/problems/DCEPC501/ (3) //NICE & EASY

http://www.spoj.com/problems/NUMTSN/ (4) //NICE &mdash; Thinking or Opti

http://www.spoj.com/problems/GONE/ (4) //NICE & EASY [digits]

http://www.spoj.com/problems/RAONE/ (4) //NICE & EASY [digits] &mdash; almost similar as above

http://www.spoj.com/problems/STRSEQ/ (4) //VERY VERY NICE &mdash; Next-Function

http://www.spoj.com/problems/MYQ8/ (4) //VERY NICE &mdash; 3x3 tic-tac-toe [implementation]

http://codeforces.com/contest/859/problem/C (3) //Easy+Sympathic [PrefixSumOptional]

http://codeforces.com/contest/859/problem/D (4) //NICE [Probabilities]

http://www.spoj.com/problems/UNICA/ (4) //VERY NICE [Posibilities][Print][Classical]

http://www.spoj.com/problems/KOPC12H/ (4) //NICE Digit-DP

http://www.spoj.com/problems/DRACULA/ (4) //NICE Digit-DP (Both sides) &mdash; iterate by sum

http://www.spoj.com/problems/ABCPATH/ (3) //DP over dfs (maybe without dp works too?)

http://www.spoj.com/problems/BEHAPPY/ (2) //Easy one &mdash; low constraints

http://www.spoj.com/problems/STRCOUNT/ (4) //No input (over bits)

http://codeforces.com/contest/855/problem/B (2) //prolly not even necessary

http://codeforces.com/contest/855/problem/C (4) //dp on tree

http://codeforces.com/contest/855/problem/E (5) //VERY NICE &mdash; Digits & Bitmask & Query (learning!)

http://www.spoj.com/problems/PAINTWAL/ (6) //VERY NICE &mdash; Imho hard (opti could beat)

http://www.spoj.com/problems/ADFRUITS/ (3) //Very simple (substring == subsequence)

http://www.spoj.com/problems/MAIN113/ (2) //NICE but somehow too low constraints

http://www.spoj.com/problems/MAIN112/ (4) //NICE &mdash; Bitmask

http://codeforces.com/contest/864/problem/E (5) //VERY NICE &mdash; Sort

http://www.spoj.com/problems/NOVICE63/ (4) //NICE -On digits (binary)

http://www.spoj.com/problems/TUG/ (3) //NICE + Observation {N>100 == YES}

http://www.spoj.com/problems/DOMINO1/ (4) //Used map to solve it

http://www.spoj.com/problems/NY10E/ (2) //Easy dp

http://www.spoj.com/problems/MAIN72/ (3) //Easy knapsack

http://www.spoj.com/problems/NOVICE43/ (2) //Unbelievably low constraints

http://codeforces.com/contest/598/problem/E (4) //N^5 strategy works fine [VERY NICE]

http://www.spoj.com/problems/CHAIR/ (3) //Maybe combinatorics too?

http://www.spoj.com/problems/ACPC10D/ (3) //NICE &mdash; DAG traversal

http://www.spoj.com/problems/CPCRC1C/ (4) //Digits dp (return pair)

http://www.spoj.com/problems/BORW/ (3) //Inc+Dec sequence (small array)

http://codeforces.com/problemset/problem/16/E (5) //Bitmask [NICE]

http://codeforces.com/problemset/problem/18/E (5) //VERY NICE {no need for second iteration}

http://codeforces.com/contest/2/problem/B (5) //NICE &mdash; 2/5 are in-fact independent

http://codeforces.com/contest/4/problem/D (3) //Classical [FW works too] XY > xy

http://codeforces.com/contest/6/problem/D (4) //NICE (N^4)

http://codeforces.com/contest/321/problem/E (7) //VERY NICE &mdash; D&C Trick

http://codeforces.com/contest/868/problem/F (8) //VERY VERY NICE  D&C Trick &mdash; With MO Principal

http://codeforces.com/contest/8/problem/C (5) //NICE &mdash; Masks [N*2^N]

http://codeforces.com/contest/868/problem/E (8) //VERY NICE &mdash; HARD &mdash; on tree

http://codeforces.com/contest/10/problem/D (4) //LCIS [NICE]

http://codeforces.com/contest/13/problem/C (5) //NICE [sorting][only elements from array]

http://codeforces.com/contest/17/problem/C (5) //[NICE][iterative-sparse][+idea]

http://codeforces.com/contest/19/problem/B (4) //Knapsack (after good look)

http://codeforces.com/contest/30/problem/C (4) //Probabilities + (slight)GEO

http://codeforces.com/contest/31/problem/E (4) //[NICE]

http://codeforces.com/contest/41/problem/D (4) //With printing

</spoiler>

<spoiler summary="dsu">

http://www.spoj.com/problems/ADABRANC/

https://www.spoj.com/problems/CONSEC/ (4) //[NICE][OFFLINE]

https://codeforces.com/gym/102006/problem/C (4) //[NICE][BRUTE-FORCE]

http://codeforces.com/gym/101962/problem/J (5) //[VERY NICE][TREE-FAT][SPARSE]

http://codeforces.com/contest/915/problem/F (6) //[VERY NICE][SORTING]

http://codeforces.com/contest/141/problem/E (6) //[NICE][SPANNIG TREE]

7903 - Pandaria (7) //[VERY NICE][DSU][SORTING][MERGE][DFS]

http://codeforces.com/contest/110/problem/E (4) //[NICE][COMBINATORICS][TREE]

http://codeforces.com/contest/90/problem/E (5) //[NICE][DSU-LIKE-LINKS][SIMULATION]

http://codeforces.com/contest/87/problem/D (5) //[VERY NICE][SORTING][COMPRES][DFS]

http://codeforces.com/contest/884/problem/E (5) //[VERY NICE][MEMORY SPARSE]

http://codeforces.com/contest/60/problem/D (6) //[NICE][Pythagorean Triples][Gen over max!]

UVA	10947

UVA	12363

LA	3833

http://codeforces.com/problemset/problem/742/D  //+DP

UVA	10178

http://codeforces.com/contest/723/problem/F 7

13153 UVA (5)

13169 UVA (3)

11987 UVA (3)

11474 UVA (4)

http://www.spoj.com/problems/BTCODE_G/

http://codeforces.com/problemset/problem/691/D

Gym	101174K [2016-2017 ACM-ICPC Southwestern European Regional Programming Contest (SWERC 2016)]

UVA	10583

LightOJ	1003

http://codeforces.com/problemset/problem/731/C

UVA	793

UVA	11966

https://www.codechef.com/problems/COZIC

3939 [LA]

UVA	11503

http://codeforces.com/problemset/problem/755/C

UVA	1395

http://codeforces.com/contest/687/problem/D 6

http://codeforces.com/contest/680/problem/E 7 //+precalculation/brute force

http://codeforces.com/contest/766/problem/D 5

http://www.spoj.com/problems/LEXSTR/ (3) //Nice na stringu

http://codeforces.com/contest/805/problem/C 3 //NICE (dijkstra like :P)

http://www.spoj.com/problems/IITKWPCI/ (3) //VERY NICE

http://www.spoj.com/problems/FRNDCIRC (3) //Classical DSU (NICE for practice)

http://www.spoj.com/problems/FOXLINGS/ (3) Easy &mdash; just renumbering

http://www.spoj.com/problems/NITTROAD/ (4) //Process from back

http://www.spoj.com/problems/SHAHBG/ (2) //DSU not needes (simulated by array)

http://codeforces.com/contest/598/problem/D (3) //Can be solved with DFS too

http://codeforces.com/contest/9/problem/E (4) //Making one big cycle

http://codeforces.com/contest/25/problem/D (4) //Could be done linear too

http://codeforces.com/contest/28/problem/B (4) //NICE [imho bad statement]

http://codeforces.com/contest/876/problem/D (4) //DSU adjacent + visited

http://codeforces.com/contest/875/problem/F (6) //NICE &mdash; Maximum cactus-forest [kruskal-like]

</spoiler>

<spoiler summary="euler_function">

http://codeforces.com/gym/101879/problem/C (6) //[VERY NICE][DFS]

http://codeforces.com/contest/907/problem/F (7) //[MAGIC]

UVA	10299

UVA	10990

https://www.codechef.com/problems/SMPLSUM

https://www.codechef.com/problems/COZIE

http://www.spoj.com/problems/LCMSUM/

Gym	100975F [2003-2004 Petrozavodsk Summer Training Camp, Saratov SU Contest]

UVA	13132

http://www.spoj.com/problems/GCDEX/

UVA	12995

http://www.spoj.com/problems/TIP1/

UVA	11327

LightOJ	1007

http://www.spoj.com/problems/ETF/

Project Euler #72: Counting fractions

http://www.spoj.com/problems/DCEPCA03/

http://www.spoj.com/problems/NAJPWG/ 4 //Gauss-Euler

http://www.spoj.com/problems/DCEPC12G/ (5) //Do what is written there

http://www.spoj.com/problems/INVPHI/ (5) //Inverse euler

</spoiler>

<spoiler summary="euler_tour">

https://codeforces.com/gym/102006/problem/H (4) //[SORTING][OBSERVATION]

http://codeforces.com/gym/101650 [I](5) //[NICE][GRAPHS]// Theory is useful

13246 - Chained Words (4) //[NICE][LEXICOGRAPHICAL]

UVA	10735

http://codeforces.com/contest/789/problem/D //Adj EG + Self/everything

http://codeforces.com/contest/21/problem/D (5) //[NICE][EulerTour+DP]

http://codeforces.com/contest/36/problem/E (6) //VERY NICE [4odd is hardest]

</spoiler>

<spoiler summary="factorization">

http://www.spoj.com/problems/ADAHW/ [RHO][Number Theory]

http://www.spoj.com/problems/ADADIGIT/ [Permutations]

https://www.spoj.com/problems/PRIMEP/ (5) //[VERY NICE][SEGMENT][BS][SIEVE]

https://codeforces.com/gym/101981 [J] (4) //[NICE][DIVIDE]

http://codeforces.com/gym/101801 [B] (3)

UVA	13067

Project Euler #108: Diophantine reciprocals I

http://www.spoj.com/problems/CHGROOM/

Gym	101370A [2009-2010 Summer Petrozavodsk Camp, Petr Mitrichev Contest 5]

http://codeforces.com/problemset/problem/837/E

http://www.spoj.com/problems/PSYCHOT/

http://www.spoj.com/problems/FACTDIV/

http://www.spoj.com/problems/NOSQ/

http://www.spoj.com/problems/FCDC/

http://www.spoj.com/problems/NFACTOR/

http://www.spoj.com/problems/ABA12D/

http://www.spoj.com/problems/PSTR/

http://www.spoj.com/problems/AMR11E/

http://www.spoj.com/problems/FACT1/

http://www.spoj.com/problems/FACT2/

https://www.hackerearth.com/problem/algorithm/gold-at-lolympics/

12005 UVA (7)

12062 UVA (6)

11960 UVA (3)

http://www.spoj.com/problems/FACTCG2/ (3)

http://www.spoj.com/problems/FACT0/ (4)

http://codeforces.com/contest/546/problem/D 5

http://codeforces.com/contest/222/problem/C 6

http://www.spoj.com/problems/COMDIV/ 3

http://www.spoj.com/problems/SINEGGS/ 3

http://www.spoj.com/problems/BDOI16B/ 4

http://www.spoj.com/problems/HG/ 4 //Map == OK

11099 UVA (3) //factor + recursion

13194 UVA (3) //factorize+generate /or just check

13191 UVA (6) //Pollard-Rho

http://codeforces.com/contest/818/problem/E (4) // Efficient + Two Pointers

http://codeforces.com/contest/831/problem/F (6) //MAGIC

http://codeforces.com/contest/839/problem/D (4) // Combinatorics + IE

http://www.spoj.com/problems/SAS002/ (5) //Find all divisors (big numbers)

http://www.spoj.com/problems/GCDS/ (4) //Lowest unused prime

http://www.spoj.com/problems/IITKWPCF/ (4) //Nonprime divisors of N/2

http://codeforces.com/contest/851/problem/D (4) //Properties of GCD + factor: NICE

http://www.spoj.com/problems/PTIME/ (3) //Low bounds &mdash; check each prime independently

http://www.spoj.com/problems/MAIN12B/ (3) //NICE [Factorization][Sort][Unique]

http://www.spoj.com/problems/AMR11E/ (2) //2664 is the biggest

http://www.spoj.com/problems/GCPC11A/ (4) //Very nice &mdash; factorize + divide N by powers

http://www.spoj.com/problems/AMR10C/ (3) //Maximum of factor-powers

</spoiler>

<spoiler summary="fenwick">

http://www.spoj.com/problems/ADABEHIVE/ [2D]

http://www.spoj.com/problems/ADACABAA/ [2D][Sparse]

https://codeforces.com/contest/1191/problem/F (5) //[NICE][SORTING]Or similar DS

https://codeforces.com/gym/102001/problem/H (4) //[NICE][GREEDY]

https://toph.co/p/easy-prime (4) //[EASY][SIEVE]

https://toph.co/p/mario-and-princess-peach (5) //[NICE][DP][SEGMENT TREE][MAX]

http://codeforces.com/gym/101628/problem/B (5) //[NICE][SPARSE][STL]

http://codeforces.com/gym/100112 (4) [B] //[NICE][INVERSION][OBSERVATION]

http://codeforces.com/gym/101982 (7) [I] //[VERY NICE][INVERSION][OBSERVATION]

http://codeforces.com/gym/101908/problem/C (4) //[MATH][INVERSION]

http://codeforces.com/gym/101889 (5) //[NICE] normalize

DevSkills-422: Double Pairs (4) //[NICE] normalize

7591 - Distribution Center (4) //[NICE][SORTING]

http://codeforces.com/contest/903/problem/D (5) //[NICE][BIG]

http://codeforces.com/contest/102/problem/D (4) //[NICE][+DP][NORMALIZE]

http://codeforces.com/gym/101047/problem/J [2D]

http://www.spoj.com/problems/MATSUM/ [2D]

https://www.hackerearth.com/practice/data-structures/advanced-data-structures/fenwick-binary-indexed-trees/practice-problems/algorithm/counting-in-byteland/ [3D]

https://devskill.com/CodingProblems/ViewProblem/300

http://codeforces.com/contest/707/problem/E 7 [2D]

http://codeforces.com/contest/749/problem/E 8

http://codeforces.com/problemset/gymProblem/101055/D 5 [2D]

11240 UVA (4)

http://codeforces.com/contest/459/problem/D (4) //[NICE][SWEEPING]

http://codeforces.com/contest/61/problem/E (4) //[NICE][CLASSICAL][2*FW][NORMALIZE]

http://codeforces.com/contest/669/problem/E 5 //fenwicks &mdash; sparse

http://codeforces.com/contest/777/problem/E 4 //MAXIMUM

http://www.spoj.com/problems/TULIPNUM/ 4 //inc &mdash; 1 nor+num|sum(A[B],A[E])

http://codeforces.com/contest/799/problem/C 3 //MAX FW (but possibly easier?)

http://codeforces.com/contest/831/problem/E 4 //MAP to get ORDER &mdash; FW == LIST

http://www.spoj.com/problems/SAS001/ (4) //Nice &mdash; number of inversions + 2P

http://www.spoj.com/problems/TPGA/ (4) //NICE &mdash; Lesser*(N-i-1)!

http://www.spoj.com/problems/SGIFT/ (4) //BS works too

http://www.spoj.com/problems/SUMSUM/ (5) //Bit-by-Bit cnt 0/1

http://www.spoj.com/problems/AKVQLD03/ (3) //Classical fenwick &mdash; easy

http://www.spoj.com/problems/ZIGZAG2/ (6) //Very nice &mdash; FW + BS + DP

http://codeforces.com/contest/849/problem/E (7) //2D Fenwick / ST+TP [NICE]

http://www.spoj.com/problems/CRAYON/ (5) //VERY NICE [2*FW &mdash; begin + end]

http://www.spoj.com/problems/NITT8/ (4) //Norm. + Store indices in MAX-Fenwick [REVERSE] [VERY NICE]

http://www.spoj.com/problems/DCEPC705/ (4) //NICE! Sort + Fenwick

http://www.spoj.com/problems/DCEPC206/ (3) //NICE & EASY <or many other approaches>

http://www.spoj.com/problems/KOPC12G/ (4) //N Fenwick trees

http://www.spoj.com/problems/TRIPINV/ (4) //2xFenwick (triples counting)

http://codeforces.com/contest/597/problem/C (4) //[VERY NICE] 11*Fenwick

http://codeforces.com/contest/12/problem/D (4) //NICE [triplet-comparing][sort]

https://www.spoj.com/problems/NARHIL/ // Sugested by [user:ak07]

</spoiler>

<spoiler summary="fft">

http://www.spoj.com/problems/ADAMATCH/

https://toph.co/p/play-the-lottery (7) //[VERY NICE][D&C][MODULAR]

UVA	12633

6886 &mdash; Golf Bot [LA]

http://www.spoj.com/problems/POLYMUL/en/

Gym	100960C [2015-2016 Petrozavodsk Winter Training Camp, Nizhny Novgorod SU Contest]

https://www.codechef.com/problems/APRPS

https://www.codechef.com/problems/POLYEVAL

http://www.spoj.com/problems/TSUM/ 5

13182 UVA 5 //ACTG hamming

http://codeforces.com/contest/827/problem/E (8) //MAGIC

http://www.spoj.com/problems/MAXMATCH/ 5 //abc hamming

</spoiler>

<spoiler summary="flow">

https://www.spoj.com/problems/DISGRAPH/ (5) //Stoer-Wagner [global]

https://codeforces.com/gym/101981 [I] (4) //[NICE]

http://codeforces.com/gym/101982 [E] (5) //[VERY NICE][GRID]

http://codeforces.com/gym/101845/problem/F (4) //Basic

http://codeforces.com/gym/101908/problem/G (4) //[NICE][MATCHING][BS]

http://www.spoj.com/problems/FASTFLOW/en/ //Raw (no sauce)

http://codeforces.com/contest/78/problem/E (5) //NICE [Matching-like][+BFS]

4322 — Destroying the bus stations (Live Archive)

11380 — Down Went The Titanic (UVA) //Interesting grid problem

6395 — Surely You Congest (LA) //VERY NICE [slightly advanced]

7204 — Blood groups (LA)

http://codeforces.com/gym/100963 (Flame of Nucleus — F)

11167 — Monkeys in the Emei Mountain //Also harder (imho)

http://codeforces.com/problemset/problem/653/D (+BS)

13000 — VIP Treatment (+BS)

1242 — Necklace

https://www.deadline24.pl/assets/problemsets/dl24.elim.2017.B.en.pdf (DEADLINE 24 problem — not sure if it can be submited :O)

3487 — Duopoly (Near matching)

http://codeforces.com/problemset/problem/727/D

http://codeforces.com/problemset/problem/704/D [Also advanced]

5418 — A Plug for UNIX (LA)

4957 — Fake scoreboard (LA) //If I remember well, other solutions was also possible

1155 — Power Transmission (LOJ) //(classical)

https://www.codechef.com/problems/ROBOTDAG //Ford-Fukherson

10804 — Gopher Strategy (UVA)

11506 — Angry Programmer (UVA) //Nodes division

10511 — Councilling (UVA)

563 — Crimewave

1306 — The K-League (UVA)

1345 — Jamie's Contact Groups

10092 — The Problem with the Problem Setter

Problem B. Roller Coaster Scheduling (GCJ — 2017)

259 — Software Allocation (UVA)

5905 — Pool construction (LA) //Imho harder

10480 — Sabotage

http://codeforces.com/contest/808/problem/F 6 //NICE &mdash; nontrivial (max matching with bigger flows)

http://codeforces.com/contest/847/problem/J 6 //Probably not flows &mdash; matching-like

</spoiler>

<spoiler summary="flow-matching-like">

http://www.spoj.com/problems/ADAHOSE/ [DUAL-GRAPH]

http://codeforces.com/contest/903/problem/G (6) //[VERY NICE][SEG-TREE][CUT]

3837 [LA] //Stable Marriage

UVA	1175 //Stable Marriage

11594 — All Pairs Maximum Flow (UVA)

http://www.spoj.com/problems/ADABLOOM/ //Maximum matching in general graph

11439 — Maximizing the ICPC //Maximum matching in general graph

1376 — Animal Run //Max flow on planar graph (Dual == shortest path over edges)

10989 — Bomb, Divide and Conquer //Stoer-Wagner — global cut

</spoiler>

<spoiler summary="floyd-warshall">

https://codeforces.com/contest/1204/problem/C (4) //[DP] Nice but hard statement

https://codeforces.com/contest/1202/problem/B (3) //[VERY NICE]

http://codeforces.com/gym/101845/problem/C

https://www.urionlinejudge.com.br/judge/en/problems/view/2676 (3) //simple FW

10724 UVA

UVA	117

http://codeforces.com/problemset/problem/21/D

UVA	1198

LightOJ	1086 //+DP

http://www.spoj.com/problems/INGRED/ //+DP

UVA	10048

UVA	125

Gym	101223C [2017 Facebook Hacker Cup, Round 1] //+DP

LightOJ	1221

UVA	423

UVA	12179 //+DP

UVA	1416

UVA	1233

UVA	10793

10099 UVA

UVA	869

LightOJ	1174

http://www.spoj.com/problems/ARBITRAG/ //Other algos shall work too

13211 UVA (5) //NICE &mdash; FW adding states

http://www.spoj.com/problems/ROHAAN/ (3) //Classical

http://codeforces.com/contest/25/problem/C (4) //Adding new edges .. need FW principal

http://codeforces.com/contest/33/problem/B (3) //NICE [dijkstra could work too]

</spoiler>

<spoiler summary="friedvaldAlgorithm">

http://www.spoj.com/problems/ADAPOWER/

4956 [LA]

</spoiler>

<spoiler summary="game_theory">

http://www.spoj.com/problems/ADAGAME/ [DP]

http://www.spoj.com/problems/ADAGAME2/

http://www.spoj.com/problems/ADAGAME4/

http://www.spoj.com/problems/ADAQUBIC/

http://www.spoj.com/problems/ADAFIMBR/

http://www.spoj.com/problems/ADAGAME5/

http://www.spoj.com/problems/ADAXMAS/

https://codeforces.com/contest/1194/problem/D (4) //[OBSERVATIO][PATTERN]

https://codeforces.com/contest/1191/problem/E (4) //[NICE][IF][OBSERVATION]

https://www.spoj.com/problems/HUSGAME/ (4) //[VERY NICE][OBSERVATION][RECURSION]

https://www.spoj.com/problems/IBIGAME/ (5) //[VERY NICE][OBSERVATION][DP]

https://codeforces.com/gym/101981 [A] (4)

https://codeforces.com/gym/102058/problem/F (4) //[NICE]

http://codeforces.com/gym/101801 [F] (3) //[EASY][OBSERVATION][NIM]

http://codeforces.com/gym/101908/problem/B (5) //[NICE][NIMBERS][OBSERVATION]

http://codeforces.com/gym/101873 [H] (5) //[VERY NICE][OBSERVATION][TREE] //LUP LUP

http://codeforces.com/gym/101808/problem/I (5) //[DP][OBSERVATION]

http://codeforces.com/contest/919/problem/F (6) //[NICE][HARD][IMPLE][BFS][TOPO][GRAF]

http://codeforces.com/contest/918/problem/D (4) //[NICE][DAG][DP][TREE]

http://codeforces.com/contest/914/problem/B (3) //[NICE][EASY][OBSERVATION][PARITY]

http://codeforces.com/contest/148/problem/D (4) //[EASY][DP][PROBABILITY]

http://codeforces.com/contest/138/problem/D (7) //[VERY NICE][DP][OBSERVATION]

https://arc087.contest.atcoder.jp/tasks/arc087_c (5) //[VERY NICE][TRIE][SEQUENCE]

http://codeforces.com/contest/120/problem/E (3) //[NICE][SYMETRY][PARITY]

http://codeforces.com/contest/88/problem/E (5) //[VERY NICE][PREFIX-XOR][NIMBERS][SQRT][MATH]

http://codeforces.com/contest/69/problem/D (4) //[NICE][DP] Reflection can be ignored

http://codeforces.com/contest/55/problem/C (4) //[NICE] Size of piece from border

http://codeforces.com/problemset/problem/255/E --MEX

https://devskill.com/CodingProblems/ViewProblem/91

https://devskill.com/CodingProblems/ViewProblem/364

Project Euler #96: Su Doku //Sudoku

11859 UVA 4

11863 UVA 4

11892 UVA 3 //Probably solved by many

11534 UVA 5

http://www.spoj.com/problems/VECTAR11/ 4 //Nsqrt(N) passes [with break]

http://codeforces.com/contest/768/problem/E (4) //NICE &mdash; Grundy

http://www.spoj.com/problems/SYNC13C/ (4) //2*DP {maybe not seeing sth}

http://codeforces.com/contest/787/problem/C (4)

http://codeforces.com/contest/794/problem/C (3) //Find optimal strategy: choose back/front

http://codeforces.com/contest/794/problem/E (5) //NICE Find stategy: Even/Odd

http://codeforces.com/contest/812/problem/E (7) //Advanced NIM strategy

http://www.spoj.com/problems/GAMEMVS/ (4) //Nimbers (Ai^X)<=Ai

http://www.spoj.com/problems/PLAYGAME/ (3) //Check pattern

http://www.spoj.com/problems/CHAOS_CC/ (4) //VERY NICE [nimbers]

http://codeforces.com/contest/851/problem/E (5) //Very nice [nimbers] [bitset]

http://www.spoj.com/problems/CHGROOM/ (4) //+Factorisation [NICE & Easy]: Win unless 2 prime factors

http://www.spoj.com/problems/EALP1/ (4) //NICE ~ Possible Moves of NIM

http://www.spoj.com/problems/GAME3/ (4) //VERY NICE &mdash; pattern watching [A145812]

http://www.spoj.com/problems/GAME2/ (5) //VERY NICE &mdash; https://community.topcoder.com/tc?module=Static&d1=match_editorials&d2=srm338 (CAKE)

http://www.spoj.com/problems/CF36D/ (5) //Pattern watching (care for 1)

http://codeforces.com/contest/15/problem/C (4) //VERY NICE [XOR: A,1,A+1,0..repeat]

http://codeforces.com/contest/39/problem/E (4) //Slightly [DP][MATH][ROUNDING]

http://codeforces.com/contest/63/problem/E (5) //[NICE][BITMASK-DP]

</spoiler>

<spoiler summary="gauss">

12910 &mdash; Snakes and Ladders [UVA]

UVA	10828

http://codeforces.com/gym/100923/problem/C

4963 [LA]

UVA	12849

Gym	100962A [2015-2016 Petrozavodsk Winter Training Camp, Moscow SU Trinity Contest][NICE]

UVA	10109 [NICE][HARD-WORK]

</spoiler>

<spoiler summary="geometry">

http://www.spoj.com/problems/ADAPICK/

http://www.spoj.com/problems/ADAKOHL/

https://codeforces.com/gym/102307/problem/A (7)

https://codeforces.com/contest/1199/problem/B (2) //[NICE][SIMPLE]

https://codeforces.com/gym/101991/problem/J (5)

https://codeforces.com/gym/101991/problem/B (4)

https://codeforces.com/gym/102006/problem/I (4) //[VERY NICE][ITERATIVE]

https://codeforces.com/gym/102021 [G] (8) //[3D]

https://codeforces.com/gym/102021 [B] (5) //Path on circle

https://codeforces.com/gym/102058/problem/K (3) //[BRUTE-FORCE][FAIL]

https://codeforces.com/gym/101972/problem/C (4) //[EASY][POINTS DISTANCE][IMAGE]

http://codeforces.com/gym/101628/problem/C (4) //Circles intersection

http://codeforces.com/gym/100112 [G] (4) //Special cases and so on - imple.

http://codeforces.com/gym/101982 [G] (3) //[DISTANCE]

http://codeforces.com/gym/101845/problem/D (5) //[VERY NICE][POLYGON][MO]

http://codeforces.com/gym/101962/problem/G (5) //Angles

http://codeforces.com/gym/101908/problem/K

http://codeforces.com/gym/101879/problem/A (7)

http://codeforces.com/gym/101873 [G] (4) //Pick's Theorem

http://codeforces.com/gym/101873 [A] (6) //heavy implementation

http://codeforces.com/gym/101808/problem/E (5)

http://codeforces.com/gym/101808/problem/A (2)

http://codeforces.com/gym/101666 [A] (4)

http://codeforces.com/gym/101726/problem/J (5) //[NICE][INTERSECTION][DS]

http://codeforces.com/gym/101650 [F] (6) //Polygons + circles

http://codeforces.com/gym/101650 [H] (2) //A few if's

http://codeforces.com/contest/908/problem/C (3)

http://codeforces.com/contest/140/problem/A (3) //Circles around bigger circle

http://codeforces.com/contest/136/problem/D (4) //+Brute-Force

http://codeforces.com/contest/127/problem/A (1) //Points distance

http://codeforces.com/gym/101597/problem/B (3) //Simply  brute-force just the closest to points

http://codeforces.com/contest/70/problem/D (5) //Dynamic Convex Hull

https://icpc.kattis.com/problems/airport //Proposed by [user:tautsjasiunsas]

https://www.hackerrank.com/contests/world-codesprint-7/challenges/elastic-rope/problem

https://devskill.com/CodingProblems/ViewProblem/20 [EASY]

UVA	10321 //Polygon intersection

UVA	11265 //Polygon point +/-

UVA	13112 //Polygon

10907 UVA [Area of polygon from a point]

3378 &mdash; Swamp Things [LA] &mdash; Maximum points on line

UVA	11768 //Discrete points

2542 [LA] //Arc size [formula]

UVA	1571 //As below [easier]

https://www.codechef.com/problems/ALLPOLY //[NICE] Point seeing polygon

http://www.spoj.com/problems/IITKWPCL/ //Point distance

UVA	11281 //circle~triangle

UVA	12921 //circle reconstruction

UVA	190 //circle from 3 points

UVA	12240 //pts>circle

UVA	438 //circle pt

LightOJ	1018 //Minimum # of lines through all pts [VERY NICE]

UVA	11008 //Similar as above

UVA	12830 //Biggest rectangle without points inside

UVA	11012 //Most distant points

UVA	1683 //Closest points

UVA	12389 //3D MH Closest Points

http://www.spoj.com/problems/AMR12C/ //Pt closest to all other points

http://www.spoj.com/problems/CLOPPAIR/ //Closest pair of points

UVA	10678 //Circles intersection

http://codeforces.com/problemset/problem/600/D //Circles intersection

LightOJ	1118 //Circles intersection

http://www.spoj.com/problems/CERC07C/en/ //Bounding circle

UVA-10005 //Bounding circle

2407 [LA] //Bounding Sphere

LightOJ	1120 //Rectangle's Union

LightOJ	1130 //Circle x Rectangle intersection

UVA	11177 //Circle x Convex Polygon

http://codeforces.com/problemset/problem/610/D //Lines intersections (axes parallel)

6263 [LA] //Pt in areas

LightOJ	1058 //# parallelograma

UVA	12931 //Common area of polygons

UVA	10301 //Intersecting circles

UVA	453 //Circles intersection

http://codeforces.com/problemset/problem/681/E //Circles intersection

UVA	920 //Lines intersecion (etc..)

UVA	12556

http://codeforces.com/problemset/problem/793/C //Intersection ans similar

UVA	11343 //Intersection of segments

UVA	866 //Intersection of segments

Gym	100190I [2011 ACM-ICPC East Central North America (ECNA 2011)] //Segment intersection

http://codeforces.com/gym/100917/problem/K

UVA	11686 //Segment intersection

LightOJ	1388

UVA	833 //Segment intersection

LightOJ	1196 //Points sides

UVA	10167 //Points sides

UVA	12818 //Arc & Point distance

http://www.spoj.com/problems/SICRANO/ //Point-line distance

http://codeforces.com/problemset/problem/614/C //Point-line distance

UVA	13117 //Point-line distance

UVA	12483 //Point-line distance

UVA	12173  //Point-line distance

UVA	10075 //Point distance on sphere

https://www.hackerrank.com/contests/booking-hackathon/challenges/nearby-attractions/problem //Pt sphr

UVA	535 //Point distance on sphere

UVA	10897 //Sphere tavelling

UVA	11817 //Sphere travelling

UVA	10316 //Sphere travelling

UVA	1469 //Fractions distance 3D

11930

12173 UVA 3

12194 UVA 4

11894 UVA 3

11769 UVA 7

11665 UVA 5

11509 UVA 4

11355 UVA 5

11265 UVA 6 //Nice one | polygon &mdash; cut/pt-check/area

11123 UVA 4 //Counting trapezoids

11177 UVA 6 //BS+Polygon/Circle intersection

11186 UVA 3

11008 UVA 5 //with DP → #intersected triangles

11012 UVA 5 //Nejvzdálenější body (Manhatton 3D)

11072 UVA 4 //Points v poly gonu

http://codeforces.com/problemset/problem/682/E 6 (biggest triangle)

http://codeforces.com/contest/672/problem/C 4 //easy &mdash; just think it up

http://codeforces.com/contest/667/problem/A 2 //vzorecky

http://codeforces.com/contest/793/problem/C 5 //EASY but beware of epsilons (NICE)

http://codeforces.com/contest/794/problem/B 2 //Can be done with BS

http://codeforces.com/contest/814/problem/D 5 //+DP on trees (NICE &mdash; but low geom.)

10750 UVA 3 //Closest points &mdash; try all pairs

http://codeforces.com/contest/820/problem/B 3 //Polygon angle find!

13213 UVA 5 //VERY NICE &mdash; Voronoi diagram (low constraints so not actually needed)

13215 UVA 3 //EASY &mdash; Sum areas and find side lengths

http://www.spoj.com/problems/IITKWPCC/ (5) //VERY VERY NICE &mdash; Nqrt(N)log(N)

http://www.spoj.com/problems/NNS/ (5) Closest points query [fake geometry] {__128}[NICE]

http://codeforces.com/contest/849/problem/B (3) //X-Product &mdash; side

http://www.spoj.com/problems/AMR12C/ (5) //Point closest to all other points (with speed)

http://www.spoj.com/problems/SICRANO/ (3) //Line-Point distance

http://www.spoj.com/problems/VCIRCLES/ (5) //Heavy geometrical ****

http://www.spoj.com/problems/CIRU/ (5) //Same as above [yet bigger constraints]

http://www.spoj.com/problems/THREETW1/ (4) //Fermat point search

http://www.spoj.com/problems/CLOPPAIR/ (4) //Closest pair of points

http://www.spoj.com/problems/MAXLN/ (2) //Some basic (4*r^2+.25)

http://www.spoj.com/problems/KOLICA/ (4) //VERY NICE [nasty iff party]

http://codeforces.com/contest/598/problem/C (4) //NICE ~ Precision! [ld]

http://codeforces.com/contest/18/problem/A (2) //EASY&FINE: Pythagoreas

http://codeforces.com/contest/40/problem/A (2) //[EASY][DISTANCE]

</spoiler>

<spoiler summary="graph">

https://codeforces.com/contest/1182/problem/D (5) //[CENTRUM][OBSERVATION][DFS]

https://www.urionlinejudge.com.br/judge/en/problems/view/1562 (5) //[VERY NICE][QUEUE][GREEDY]

https://codeforces.com/gym/102001/problem/G (4) //[NICE][BS]

https://codeforces.com/gym/102006/problem/G (4) //[NICE][TOPOSORT][OBSERVATION]

https://codeforces.com/gym/102058/problem/B (6) //[VERY NICE][REVERSE-SIMULATION]

http://codeforces.com/gym/101666 [H] (6) //[VERY NICE][GEOMETRY][DSU][EULER][PLANAR]

2827 [LA] //3Coloring

2243 [LA] //3Coloring

5603 [LA] //Coloring

UVA	1658 //Shortest paths

UVA	12821 //Shortest paths

http://codeforces.com/contest/27/problem/D (5)

11387 (UVA) 4

http://www.spoj.com/problems/VFRIEND2/ (5) //Graph possible check

http://codeforces.com/contest/859/problem/E (4) //VERY NICE (2 cases: CYCLE [x2] / TREE [x(Size+1)]

http://codeforces.com/contest/847/problem/C (2) //Forest making Easy&Nice

http://codeforces.com/contest/863/problem/C (3) //Cycle in states

</spoiler>

<spoiler summary="greedy">

https://codeforces.com/contest/1207/problem/B (3) //[NICE][EASY][IMPLE]

https://codeforces.com/contest/1204/problem/B (2) //[OBSERVE][MATH]

https://codeforces.com/contest/1148/problem/E (5) //[NICE][SORTING][STL]

https://codeforces.com/contest/1175/problem/D (4) //[NICE][PREPROCESS][SORTING]

https://codeforces.com/contest/1203/problem/F1 (5) //[VERY NICE][SORTING][CASES]

https://codeforces.com/contest/1176/problem/C (3) //[SIMPLE][NICE][IMPLE]

https://codeforces.com/contest/1176/problem/A (1)

https://codeforces.com/contest/1200/problem/B (3) //[SIMPLE][NICE]

https://codeforces.com/contest/1202/problem/A (2)

https://codeforces.com/contest/1181/problem/B (4) //[BIG]

https://atcoder.jp/contests/abc136/tasks/abc136_c (3) //[REVERSE]

https://codeforces.com/contest/1185/problem/C2 (4)

https://codeforces.com/contest/1185/problem/B (2) //[EASY]

https://codeforces.com/contest/1180/problem/B (3) //[IMPLEMENTATION][MATH]

https://codeforces.com/contest/1186/problem/D (4) //[IMPLEMENTATION]

https://codeforces.com/contest/1197/problem/B (3) //[BITONIC][IMPLE]

https://www.spoj.com/problems/DIVSTR/ (3) //[CUTE]

https://codeforces.com/gym/101981 [E] (5)  //[NICE][NORMALIZE][STACK]

https://codeforces.com/gym/102001/problem/L (3) //[BITS]

https://toph.co/p/passwords (2)

http://codeforces.com/gym/100112 (3) //[FINE]

http://codeforces.com/gym/101666 (4) //[NICE][QUEUE][DFS][EVENTS]

http://codeforces.com/gym/101806/problem/T (5) //[NICE][SEGMENT TREE][SORTING]

http://codeforces.com/contest/916/problem/B (3) //[BITS] FIRST & LAST

http://codeforces.com/contest/913/problem/C (3) //+[DP]

http://codeforces.com/contest/146/problem/D (4) //[NICE][CONSTRUCTION]

http://codeforces.com/contest/146/problem/C (3) //[EASY][NICE][TWO-CASES]

http://codeforces.com/contest/139/problem/D (4) //Muchas cases

7887 - Back to the Future (4) //[NICE][2*HEAP]

http://codeforces.com/contest/910/problem/A (2) //DP works too

http://codeforces.com/contest/125/problem/D (4) //Limited possibilities

http://codeforces.com/contest/902/problem/A (2) //Just keep last

http://codeforces.com/contest/898/problem/D (4) //[NICE][FENWICK/OR/PREFIX]

http://codeforces.com/contest/118/problem/C (4) //[NICE] - Try each digit (iterate in waves)

7706 - Pokemons (2) //Sweep and keep maximum

http://codeforces.com/contest/893/problem/D (4) //[NICE][SWEEP][MAXIMUM] - pay max when have to

http://codeforces.com/contest/892/problem/B (2) //Sweep from back

http://codeforces.com/contest/102/problem/C (3) //sort by frequency

https://devskill.com/CodingProblems/ViewProblem/419 (2) //Sweep from back

http://codeforces.com/contest/890/problem/C (3) //frequence

http://codeforces.com/contest/890/problem/B (2) //[EASY][REVERSE]

http://codeforces.com/contest/888/problem/B (2) //Equalize U/D and L/R

http://codeforces.com/gym/101597/problem/J (4) //[NICE][SWEEP]

http://codeforces.com/contest/76/problem/B (4) //[NICE][MATCHING-LIKE][2PTRS]

http://codeforces.com/contest/73/problem/B (4) //[IMPLEMENTATION][SORTING]

http://codeforces.com/contest/883/problem/K (4) //Nice - Two sweeps

http://codeforces.com/contest/49/problem/D (3) //NICE - 1010101 OR 0101010 [haming]

http://codeforces.com/contest/58/problem/C (4) //NICE - group trees by slopes

http://codeforces.com/contest/729/problem/D 3

http://codeforces.com/contest/729/problem/E 4

http://codeforces.com/contest/725/problem/D 4

http://codeforces.com/contest/725/problem/F 9

http://codeforces.com/contest/732/problem/E 5

http://codeforces.com/contest/727/problem/F 6

http://codeforces.com/contest/724/problem/D 5

http://codeforces.com/contest/723/problem/C 4

http://codeforces.com/contest/719/problem/B 2

http://codeforces.com/contest/712/problem/C 3

13152 UVA (4)

http://codeforces.com/contest/746/problem/E 5

http://codeforces.com/contest/746/problem/D 3

http://codeforces.com/contest/749/problem/C 3

11737 UVA (3)

11786 UVA (4)

11630 UVA (5)

11563 UVA (4)

11491 UVA (4)

11330 UVA (3)

11089 UVA (2)

http://codeforces.com/contest/884/problem/D (4) //PQ or Sort

http://www.spoj.com/problems/SQRMINSUM/ 3 //solve-able in O(N+M)-arrayqueue

http://www.spoj.com/problems/MSCHED/ 3 //sweep from back

http://www.spoj.com/status/ns=18780683 4 //all perm + A<B<C works

http://www.spoj.com/problems/NINJA7/ (3) //sort by diff

http://www.spoj.com/problems/NINJA2/ (4) //try all possib. (26)

http://codeforces.com/contest/767/problem/E (6)

http://codeforces.com/contest/637/problem/B (3) //NICE pro prvaky

http://codeforces.com/contest/777/problem/B (3) // -||-

http://codeforces.com/contest/777/problem/D (3) //just go from end

http://codeforces.com/contest/779/problem/C (3) //NICE pro prváky

http://www.spoj.com/problems/SPCU/ (2) //Easy &mdash; zamysleni (max int = index)

http://www.spoj.com/problems/LOPOV/ (4) //sort + queue (or just queue) NICE

http://codeforces.com/contest/792/problem/E (5) //T%S<=T/S + check proper

http://codeforces.com/contest/807/problem/E (5) //NICE &mdash; put asice P2 / rest &mdash; greedy from small

http://codeforces.com/contest/799/problem/E (5) //Many queues &mdash; but NICE

http://codeforces.com/contest/808/problem/C (3) //EASY

http://codeforces.com/contest/802/problem/B (4) //Priority by "next"

10850 UVA (4) //Queue a brute-force

http://codeforces.com/contest/813/problem/A (1) //Zahrivacka pro prvaky

10716 UVA (4) //NICE &mdash; always find closest pair

http://codeforces.com/contest/816/problem/C (3) //NICE &mdash; greater<lesser side

http://codeforces.com/contest/820/problem/D (5) //VERY NICE &mdash; O(N) -~- 5 events per number

http://codeforces.com/contest/818/problem/B (2) //Zahrivacka pro prvaky

http://codeforces.com/contest/822/problem/C (4) //Almost classical Sort+Queue

http://codeforces.com/contest/825/problem/C (2) //Nice & Easy

http://codeforces.com/contest/825/problem/D (3) //Update by modulo

http://codeforces.com/contest/835/problem/B (2) // Zahhrivacka pro prvaky

http://codeforces.com/contest/839/problem/B (3) //Nasty iffs &mdash; yet nice excersize

http://www.spoj.com/problems/PCPC12I/ (4) //Swipe MINIMUM from left/right [10^6-A[i] trick]

http://www.spoj.com/problems/AMR12I/ (3) //NICE a) MAX_SEG>=K b) (SEG_SIZE-1)/K+1

http://www.spoj.com/problems/BUSYMAN/ (2) //NICE&EASY &mdash; Sort + keep minimum

http://codeforces.com/contest/861/problem/C (3) //2+ but not same

http://www.spoj.com/problems/WORKB/ (3) //Simple "min" formula for each neighbor

http://codeforces.com/contest/864/problem/D (4) //VERY NICE &mdash; Frequency + unused

http://www.spoj.com/problems/ROADTRIP/ (4) //VERY NICE &mdash; Keeping last lesser

http://codeforces.com/contest/597/problem/B (3) //NICE [Classical]

http://www.spoj.com/problems/SHLIGHTS/ (4)

http://www.spoj.com/problems/MLK/ (3) //VERY NICE &mdash; Sum all prefix sums

http://codeforces.com/contest/867/problem/C (4) //NICE [IMPLE][2POINTERS][MID+EPS]

http://codeforces.com/contest/867/problem/E (5) //NICE [EASY-IMPLE][HARD-CONS]

http://codeforces.com/contest/18/problem/D (4) //+Big Integer

http://codeforces.com/contest/276/problem/D (4) //NICE &mdash; Find first mismatch bit (then 111...111)

http://codeforces.com/contest/3/problem/B (4) //Divide 1/2 [sort][2pointers]

http://codeforces.com/contest/3/problem/D (4) //?==) ..if open < 0: set max A-B to (

http://codeforces.com/contest/26/problem/B (4) // +1 ( | -1 ): -1, erase .. erase sum in the end

http://codeforces.com/contest/33/problem/A (2) //EASY [long-statement]

http://codeforces.com/contest/44/problem/E (2) //Try mins then try maxs

http://codeforces.com/contest/45/problem/D (3) //Priority-queue+'sort'

</spoiler>

<spoiler summary="hash">

http://www.spoj.com/problems/ADACLEAN/

https://codeforces.com/contest/1200/problem/E (5) //[VERY NICE]

http://codeforces.com/gym/101808/problem/B (5) //[NICE][NUMBERS]

http://codeforces.com/gym/101741/problem/K (5) //[NICE][SQRT][PATTERN MATCHING]

7979 - Red Rover (3) //[NICE] //Many other ways to solve

http://codeforces.com/contest/898/problem/F (5) //[VERY NICE]//Hash by 10

http://codeforces.com/contest/114/problem/D (4) //[NICE] //N^2Log(N) might/might-not be OK

https://www.urionlinejudge.com.br/judge/en/problems/view/1503 (7) //[NICE][BS][OPTI]

Gym	101466E [2017 ACM-ICPC, Universidad Nacional de Colombia Programming Contest][NICE]

12012 UVA 4

http://codeforces.com/contest/727/problem/E 7

http://codeforces.com/contest/718/problem/D 8

11855 UVA 4

http://codeforces.com/contest/752/problem/D 5

http://codeforces.com/contest/825/problem/F 5 //String + Periods

http://codeforces.com/contest/835/problem/D 4 //Palindromes

http://www.spoj.com/problems/CF25E/ (5) //VERY NICE [IMPLE>CONCEPT]

http://codeforces.com/contest/7/problem/D (4) //Palindromes

http://codeforces.com/contest/19/problem/C (4) //[NICE]: Not a string

</spoiler>

<spoiler summary="hull">

13300 - Ghost Hunting (4) //Hull + calipers passes

http://codeforces.com/gym/101982 [M] (7) //[VERY NICE][HULL][TERNARY]

http://www.spoj.com/problems/GARDENHU/en/

2453 &mdash; Wall [LA]

UVA	13213

UVA	11096

Gym	100792G [2015-2016 ACM-ICPC, NEERC, Moscow Subregional Contest]

https://www.codechef.com/problems/KTHCON

http://codeforces.com/problemset/problem/605/C

UVA	218

UVA 11072

11168 UVA

UVA	12307

Gym	100963I [2007-2008 Summer Petrozavodsk Camp, Japanese Contest, 2007-08-29]

UVA	11243

UVA	10256

109	SCUD Busters

UVA	13024 [NICE]

UVA	10002

Gym	100886H [2015-2016 Petrozavodsk Winter Training Camp, Saratov SU Contest]

UVA	1139

UVA	681

UVA	811

https://www.codechef.com/problems/MGCHGEOM

UVA	11769 //3D

</spoiler>

<spoiler summary="chess">

http://www.spoj.com/problems/ADACHESS/

http://www.spoj.com/problems/ADACHES2/

http://www.spoj.com/problems/ADAGAME5/

http://www.spoj.com/problems/ADAXMAS/

URI 1100 (3) //[BFS][KNIGHT]

https://www.codechef.com/problems/CHQUEENS (4) //[IMPLEMENTATION]

http://codeforces.com/contest/131/problem/E (4) //[NICE][STL][SORTING][QUEEN]

http://codeforces.com/contest/42/problem/B (4) //NICE - Checkmate check

UVA	10748 //bfs

LightOJ	1143

https://www.hackerearth.com/practice/algorithms/greedy/basics-of-greedy-algorithms/practice-problems/algorithm/harry-and-ron-play-a-game-of-chess/

UVA	10196

http://www.spoj.com/problems/KNMOVE/

UVA	11352

http://www.spoj.com/problems/NAKANJ/ //BFS

LightOJ	1010

LightOJ	1171 //MM

2883 LA

UVA	439

http://www.spoj.com/problems/TRKNIGHT/ //??

2308 LA

http://www.spoj.com/problems/CCHESS/ //Dijkstra

http://codeforces.com/problemset/problem/630/H //[ROOKS][BIG][COMBINATORICS]

LightOJ	1005 //As above (but with real rooks)

LightOJ	1061 //Placing queens

UVA	11085

UVA	10094 //Queen placing [NICE][PATTERN]

https://devskill.com/CodingProblems/ViewProblem/383

11852  UVA (6)

http://www.spoj.com/problems/KLUG1/ (2) //Jumps of horse

http://www.spoj.com/problems/CODESPTD/ (5) //VERY NICE &mdash; DP [Queens]

http://codeforces.com/contest/3/problem/A (2) //Imple &mdash; Shortest path for king

http://codeforces.com/contest/38/problem/B (2) //NICE &mdash; Simple possition checking

</spoiler>

<spoiler summary="implementation">

https://codeforces.com/gym/102302/problem/D (3) //[2Pointers]

https://codeforces.com/gym/102307/problem/F (4) //[PARSING][PYTHON]

https://codeforces.com/contest/1207/problem/A (2) //[MIN/MAX][MATH]

https://codeforces.com/contest/1206/problem/A (2) //[OBSERVATION]

https://codeforces.com/contest/1148/problem/A (1) //[IF][MATH]

https://codeforces.com/contest/1203/problem/A (1) //[FOR][IF]

https://codeforces.com/contest/1173/problem/A (1) //[IF]

https://devskill.com/CodingProblems/ViewProblem/584 (2)

https://codeforces.com/contest/1200/problem/A (2) //[EASY]

https://codeforces.com/contest/1182/problem/B (3) //[PRACTICE][GRID-MOVEMENT]

https://codeforces.com/contest/1201/problem/B (2)

https://codeforces.com/contest/1201/problem/A (2)

https://atcoder.jp/contests/abc136/tasks/abc136_a (1)

https://codeforces.com/contest/1199/problem/A (2) //[BF]

https://codeforces.com/contest/1183/problem/A (2)

https://codeforces.com/contest/1186/problem/A (1)

https://codeforces.com/contest/1178/problem/A (2)

https://codeforces.com/contest/1195/problem/A (2) //[ARRAY]

https://codeforces.com/contest/1191/problem/A

https://www.spoj.com/problems/MOZHSLM/ (3) //Two sweeps

https://www.spoj.com/problems/OVGDEL/ (3) //[NICE][EASY][FREQUENCY]

https://www.spoj.com/problems/VTV1001/ (2)

https://codeforces.com/gym/102001/problem/D (3)

https://codeforces.com/gym/102021 (7) //[VERY NICE]Easy thought but nice imple

https://codeforces.com/gym/101972/problem/E (2)

https://codeforces.com/gym/101972/problem/D (1) //[IF]

https://toph.co/p/full-pyramid (1)

http://codeforces.com/gym/101992/problem/F (2)

http://codeforces.com/gym/101628/problem/D (3)

http://codeforces.com/gym/100112 [I] (5) //[NICE][STRINGS][BITMASKS]

http://codeforces.com/gym/100112 [A] (2)

http://codeforces.com/gym/101982 [L] (3)

http://codeforces.com/gym/101982 [J] (2)

http://codeforces.com/gym/101982 [A] (2) //Easy

http://codeforces.com/gym/101845/problem/H (2) //Dates

http://codeforces.com/gym/101801 [L] (1)

http://codeforces.com/gym/101801 [A] (1)

http://codeforces.com/gym/101864 [C] (2) //Easy

http://codeforces.com/gym/101889/my [H] (2)

http://codeforces.com/contest/934/problem/A (2)

http://codeforces.com/contest/922/problem/A (2) //Iff-party

http://codeforces.com/contest/914/problem/A (1)

http://codeforces.com/contest/916/problem/A (2) //Time

http://codeforces.com/contest/915/problem/B (2) //Formula / Iff

http://codeforces.com/contest/915/problem/A (1)

http://codeforces.com/contest/913/problem/A (1)

http://codeforces.com/contest/912/problem/A (2) //Easy [corner-cases]

http://codeforces.com/contest/146/problem/A (1)

http://www.spoj.com/problems/ESYR/ (1) //Bad one :/

http://codeforces.com/contest/908/problem/A (1)

http://codeforces.com/contest/147/problem/A (2) //Parsing

http://codeforces.com/contest/139/problem/A (1)

http://codeforces.com/contest/137/problem/A (1)

7886 - Assigning Teams	 (2) //[EASY][SORTING]

http://codeforces.com/contest/133/problem/A (1)

http://codeforces.com/contest/134/problem/A (1)

http://codeforces.com/contest/131/problem/A (1)

http://codeforces.com/contest/127/problem/B (1) [EASY]

http://codeforces.com/contest/899/problem/B (2) //Dates

http://codeforces.com/contest/898/problem/C (3) //No thinking - just implementation

6157	How do spiders walk on water? (4)  //boring problem

http://codeforces.com/contest/900/problem/A (1)

7613	Relative atomic mass (1)

http://codeforces.com/contest/122/problem/A (1) //Find all lucky

http://codeforces.com/contest/120/problem/B (1) //Iteration

http://codeforces.com/contest/120/problem/A (1) //Iff/Logic

http://codeforces.com/contest/118/problem/B (2) //[PRINTING]

http://codeforces.com/contest/108/problem/A (1) //[EASY][PRINT][TIME]

http://codeforces.com/contest/106/problem/A (1) //Iff-party

http://codeforces.com/contest/890/problem/A (1) //if or perm

http://codeforces.com/contest/90/problem/B (2) //No idea - just cycles

http://codeforces.com/contest/75/problem/A (1) //conversion

http://codeforces.com/contest/884/problem/B (1) //Simple sum +N-1

http://codeforces.com/contest/48/problem/A (1) //Very easy [fe. perm]

http://codeforces.com/contest/51/my (2) //Lex-lowest-string (|s|=4)

http://codeforces.com/contest/54/problem/A (2) //Single sweep

http://codeforces.com/contest/719/problem/C 3

http://codeforces.com/contest/747/problem/E 4

http://codeforces.com/contest/754/problem/C 5

11482 UVA (4)

11291 UVA (3)

11070 UVA (5)  //evaluation of expression

11074 UVA (2)

http://codeforces.com/contest/678/problem/B 2 //calendar days

http://codeforces.com/contest/643/problem/A 3 //easy &mdash; just simulate

http://codeforces.com/contest/770/problem/D 5 //easy &mdash; but pain &mdash; draw

http://codeforces.com/contest/789/problem/B 3 //simulate (mby twice)

13171 UVA (1)

10800 UVA (3)

http://codeforces.com/contest/828/problem/B 2 //EASY & NICE &mdash; just analysis

http://codeforces.com/contest/825/problem/B 2 //EASY & NICE &mdash; Piskvorky &mdash; pro prvaky

http://codeforces.com/contest/837/problem/B 2 //Just implementation

http://codeforces.com/contest/837/problem/C 2 //Some nasty iffs

http://codeforces.com/contest/845/problem/B 2 //Easy pro prvaky

http://codeforces.com/contest/845/problem/D 3 //Iffs &mdash; folow the rules

http://www.spoj.com/problems/UNIHW/ 4 //NICE (but many iffs)

http://codeforces.com/contest/5/problem/A (2) //Parsing

http://codeforces.com/contest/5/problem/B (3) //Output formating

http://codeforces.com/contest/6/problem/B (2) //Simply check by adjancecy vector + set

http://codeforces.com/contest/7/problem/A (1) //Oneinteresting if

http://codeforces.com/contest/8/problem/B (2) //Sample vectors + set/or/array

http://codeforces.com/contest/12/problem/A (1) //Find mirror by middle

http://codeforces.com/contest/16/problem/A (1) //Easy check of chars

http://codeforces.com/contest/21/problem/A (2) //Easy but nasty iff imple

http://codeforces.com/contest/31/problem/B (2) //Boring imple

http://codeforces.com/contest/34/problem/C (3) //Easy string parsing

http://codeforces.com/contest/41/problem/C (2) //String parsing

</spoiler>

<spoiler summary="inclusion-exclusion">

http://www.spoj.com/problems/KPRIMESB/ (4)

http://www.spoj.com/problems/IITKWPCH/ (4) //NICE &mdash; on bits

http://www.spoj.com/problems/SUBSET/ (5) //VERY NICE &mdash; 3^10 (^2 but not exactly) (+ sorting)

https://www.hackerearth.com/practice/algorithms/dynamic-programming/bit-masking/practice-problems/algorithm/special-pairs-7/description/ (4) //NICE [Brute-force]

</spoiler>

<spoiler summary="interactive">

https://codeforces.com/gym/102307/problem/L (5) //[NICE][BS]

https://codeforces.com/contest/1207/problem/E (4) //[NICE][SIMPLE][BITS]

https://codeforces.com/contest/1206/problem/E (5) //[VERY NICE][BRUTE FORCE][DEPENDENCIES]

https://codeforces.com/contest/1174/problem/F (7) //[VERY NICE][TREE][CONSTRUCTIVE]

http://codeforces.com/contest/897/problem/D (4) //NICE! Back/Front

http://codeforces.com/contest/727/problem/C (2)

http://codeforces.com/contest/810/problem/D (4) //BS * 3 (same)

http://codeforces.com/contest/811/problem/D (4) //BFS &mdash; easy .. some ifs

http://codeforces.com/contest/835/problem/E (4) //NICE! Bitsets + Detect + XOR

http://codeforces.com/contest/844/problem/D (5) //NICE! Randomized algo

http://codeforces.com/contest/862/problem/D (4) //NICE! Find first + Binary Search

http://codeforces.com/contest/872/problem/D (4) //NICE! [no clue why it passed]

</spoiler>

<spoiler summary="isomorphism">

https://www.urionlinejudge.com.br/judge/en/problems/view/2652 (4) //Tree isomorphism

UVA	12489 //Tree

https://www.hackerrank.com/contests/hourrank-16/challenges/jenny-subtrees/problem

http://www.spoj.com/problems/DSUBTREE/ (5) //Isomorphism on trees (try all subsets)

http://www.spoj.com/problems/TREEISO/ (4) //Simple isomorphism of trees

</spoiler>

<spoiler summary="josephus">

http://codeforces.com/gym/101864 [A] (4) //Observation

UVA	151

UVA	1394

UVA	440

3803 [LA]

https://www.urionlinejudge.com.br/judge/en/problems/view/1030

UVA	12912

UVA	13114

11351 UVA (2)

http://www.spoj.com/problems/CLSLDR/ (4) //Muchas queries &mdash; go DP

http://www.spoj.com/problems/WTK/ (Easy) Suggested by [user:ayushgupta1997]

http://www.spoj.com/problems/DANGER/ (Easy) Suggested by [user:ayushgupta1997]

http://www.spoj.com/problems/POCRI/ (Medium) Suggested by [user:ayushgupta1997]

http://www.spoj.com/problems/NG0FRCTN/ (Medium) Suggested by [user:ayushgupta1997]

</spoiler>

<spoiler summary="KMP">

http://www.spoj.com/problems/ADAPET/

UVA	12604

UVA	12467

UVA	11019

http://www.spoj.com/problems/NAJPF/ (4) //classical kmp &mdash; all patterns

http://codeforces.com/contest/808/problem/G (6) //with DP -harder

</spoiler>

<spoiler summary="lca">

http://www.spoj.com/problems/ADAAPPLE/ [HLD][LCT works too]

http://www.spoj.com/problems/ADAVISIT/ [HLD]

http://www.spoj.com/problems/ADALICI/ [KTH Ancestor &mdash; FAST!]

http://www.spoj.com/problems/ADAORANG/

https://www.spoj.com/problems/COWGATH/ (5) //[VERY NICE][EULER][OFFLINE][SEGMENT]

https://codeforces.com/gym/102021 [A] (5) //[IMPLEMENTATION][LCA]

http://codeforces.com/gym/101908/problem/L (5) //[NICE][HLD][FW]

http://codeforces.com/gym/101808/problem/K (5) //[NICE][IMPLEMENTATION][CYCLE]

http://www.spoj.com/problems/LCA/ //Easiest one &mdash; low constraints [practice]

http://www.spoj.com/problems/LCASQ/

http://codeforces.com/contest/916/problem/E (6) //[VERY NICE][SEG-TREE]//REROOT

http://codeforces.com/contest/911/problem/F (5) //[VERY NICE][LONGEST PATH]

https://devskill.com/CodingProblems/ViewProblem/141

UVA	12655

https://www.codechef.com/problems/PSHTTR

LightOJ	1162

Gym	100685G [2012-2013 ACM-ICPC, NEERC, Moscow Subregional Contest]

UVA	12533

https://www.codechef.com/problems/CLOSEFAR //But kinda more comples [ST]

http://codeforces.com/contest/733/problem/F 7

11354 UVA (4)

http://www.spoj.com/problems/POLICEMEN/ (3) //simple + small graph

http://www.spoj.com/problems/QTREE2/ (5) //very easy if bin. understrood

http://codeforces.com/contest/828/problem/F 7 // Differently MST / Outside

http://codeforces.com/contest/832/problem/D (5) //Classical + Depth /OR/ HLD +ST

http://www.spoj.com/problems/DRTREE/ (5) //NICE [finding ancestor + depths]

http://codeforces.com/problemset/problem/838/B (6) //VERY NICE [HLD + ET + ST]

http://www.spoj.com/problems/NTICKETS/ (4) //Maximum on path

http://www.spoj.com/problems/GRASSPLA/ (5) //HLD

http://codeforces.com/contest/855/problem/D (4) //VERY VERY BAD STATEMENT (not so bad problem)

http://codeforces.com/gym/101630 {L}(6) //[NICE][HLD or DSU][XOR] //Parenthessis

</spoiler>

<spoiler summary="lcs_subsequence">

http://www.spoj.com/problems/ADASEED/ [HUNT]

https://codeforces.com/gym/102307/problem/C (5) //[NICE][4RUS][DP]

http://www.spoj.com/problems/MC/

UVA	10192

UVA	531

LightOJ	1110

UVA	12747 //Perm

http://www.spoj.com/problems/XMEN/ //Perm

UVA	10405

UVA	12511 //Increasing

UVA	10635 //Increasing

10949 UVA (6) &mdash; Hunt or Bit

http://www.spoj.com/problems/MC/ (3) //Classical

http://www.spoj.com/problems/LCS0/ (7) //Bit

</spoiler>

<spoiler summary="lct">

http://www.spoj.com/problems/ADAROADS/ [ONLINE][UPDATES][LCT]

http://www.spoj.com/problems/DYNALCA/en/ //DYNAMIC LCA

http://codeforces.com/gym/100460/problem/C

http://codeforces.com/gym/100960/problem/H

http://www.spoj.com/problems/DYNACON1/

http://codeforces.com/contest/892/problem/E (7) [VERY NICE]//By prices .. LCT

</spoiler>

<spoiler summary="lis">

UVA	231

UVA	10131

2931 LA

http://www.spoj.com/problems/NDS/

UVA	481

http://www.spoj.com/problems/ELIS/

UVA	497

UVA	11790

http://www.spoj.com/problems/ALTSEQ/ 3 //solvable by FW in Nlog(N)

http://www.spoj.com/problems/VISIBLEBOX/ (4) //with multiset

http://www.spoj.com/problems/DOSA/ (5)

http://www.spoj.com/problems/CODERE3/ 3 //Low bounds LIS/LDS

http://www.spoj.com/problems/BRDGHRD/ 4 //lis (nondecreasing)

http://www.spoj.com/problems/GONESORT/ 4 //Permutation-lis + riddle statement

http://codeforces.com/contest/847/problem/B 4 //Multiple Lis's

http://codeforces.com/contest/67/problem/D (4) //[NICE][DOUBLE REMAP]

</spoiler>

<spoiler summary="matching">

http://www.spoj.com/problems/ADAPATH/

http://www.spoj.com/problems/ADACITY/

http://www.spoj.com/problems/ADAPLNTS/

https://codeforces.com/contest/1198/problem/E (7) //[VERY NICE][HARD][KONIG][OBSERVATION]

URI 1330 (4) //[NICE][SIMPLE]

http://codeforces.com/gym/101873 [F] (4)

http://codeforces.com/gym/101666 [E] (6) //[NICE][GEOMETRY][BINARY SEARCH][PROBABILITY]

http://www.spoj.com/problems/MATCHING/ //Raw (no sauce)

http://codeforces.com/contest/116/problem/B (3) //Low cons. Can be done without algo

6234 — Tile Cut (LA)

10080 — Gopher II (UVA) //Easy — sympathic

11419 — SAM I AM (UVA) //Grid-Matching

http://codeforces.com/gym/101485 (Elementary Math — E) //Very nice principal [not that hard]

3673 — Black-White Grid (UVA) //Grid

12927 — Points Cover (UVA)

6851 — The Programmers (LA)

6887 — Book Club //NICE

6571 — It Can Be Arranged

12530 — Game of Tiles

http://codeforces.com/gym/100820 (Airport — A) //Nice one

http://codeforces.com/gym/100753 (Bounty Hunterr II — B) //VERY NICE — I refered multiple times to this principal

http://codeforces.com/gym/101408 (Cat vs Dog — C)

1171 — Knights in Chessboard (II) (LOJ) //Classical chess

12644 — Vocabulary

http://codeforces.com/gym/101047/problem/H

http://codeforces.com/problemset/problem/659/E

12972 — Cuban Challenge (UVA)

1201 — Taxi Cab Scheme (UVA)

12963 — Astragalus Nitidiflorus

6525 — Attacking rooks (LA)

3415 — Guardian of Decency (LA)

12159 — Gun Fight (UVA)

https://www.codechef.com/problems/CHEFYODA //Imho matching is not the crucial part here

12831 — Bob the Builder

http://codeforces.com/problemset/problem/831/D

11262 — Weird Fence

12549 — Sentry Robots

11138 — Nuts and Bolts

http://codeforces.com/contest/727/problem/D 4

11985 UVA (5)

http://www.spoj.com/problems/AMR12A/ (5) //VERY NICE [goophers + bonus] (BS)

http://www.spoj.com/problems/NITT4/ (4) //VERY NICE [Chessboard matching]

http://www.spoj.com/problems/SCPC11H/ (4)//NICE &mdash; Match those which fits inside

</spoiler>

<spoiler summary="matrix">

12045 UVA (4)

</spoiler>

<spoiler summary="matrix_exponentiation">

http://www.spoj.com/problems/ADAMONEY/

UVA 13298 - A Fibonacci Family Formula (4) //[NICE][CLASSICAL]

http://codeforces.com/gym/101628/problem/I (4) //[MODULAR][NICE][TRANSITION]

http://codeforces.com/gym/101845/problem/A

13284	Macarons (4) //[NICE][BITMASK][DP] Classical

http://codeforces.com/contest/147/problem/B (5) //[NICE][BS][GRAPHS]

http://codeforces.com/contest/107/problem/D (5) //[NICE][DP]

UVA	12653

LightOJ	1131

UVA &mdash; 12470

http://codeforces.com/problemset/problem/696/D

https://www.hackerrank.com/contests/mathemagic-bits/challenges/gp-on-fibonacci-matrix [accesable?]

https://www.hackerrank.com/contests/mathemagic-bits/challenges/degree-diameter-on-trees [accesable?]

LightOJ	1052

https://www.codechef.com/problems/KBIGNUMB

LightOJ	1160

LightOJ	1096

UVA	11486

http://codeforces.com/problemset/problem/718/C

LightOJ	1070

LightOJ	1132

http://codeforces.com/problemset/problem/621/E

Project Euler #114: Counting block combinations I

http://codeforces.com/problemset/problem/821/E

UVA	12593

https://www.codechef.com/AUG16/problems/SHAIKHGN //Not exactly but similar principle

11551 UVA (4)

11486 UVA (5)

10743 UVA (5) //A001169 [easy multi / hard to come with recurence]

http://codeforces.com/contest/821/problem/E (6) //Not trivial to come-up with matrix

http://www.spoj.com/problems/DCEPCA06/ (4) //NICE &mdash; 10x10 matrix

http://www.spoj.com/problems/GSWORDS/ (3) //NICE&EASY &mdash; 3-states "OO,OX,XO"

http://www.spoj.com/problems/TETRAHRD/ (4) //Easy + Sum

http://www.spoj.com/problems/NACCI/ (4) //Classical (N-Bonacci)

http://www.spoj.com/problems/JZPCIR/ (5) //VERY NICE: A137726

</spoiler>

<spoiler summary="mcmf">

http://www.spoj.com/problems/ADAGROW/

http://www.spoj.com/problems/ADAFEAR/

https://www.urionlinejudge.com.br/judge/en/problems/view/1617 (4) //[BASIC]

13288 - Cordon Bleu (6) //[NICE][MATCHING]

http://codeforces.com/gym/100800 (Aqueduct Construction — A)

10806 — Dijkstra, Dijkstra.

12944 — Earthquake Disaster

12891 — Risk of Trading

https://www.codechef.com/problems/HOGON

http://codeforces.com/contest/863/problem/F (5) //VERY NICE

11613 UVA (6)

http://codeforces.com/contest/802/problem/C (8) //Nice but hard to see + negative

http://codeforces.com/contest/802/problem/N (5) //Easy but faster MCMF needed

http://codeforces.com/contest/818/problem/G (6) //NICE + MUCH Faster MCMF

http://www.spoj.com/problems/BNMT/ (7) //VERY NICE (some optimalisations needed + weird data set)

http://codeforces.com/contest/884/problem/F (6) //Alphabetical buckets

</spoiler>

<spoiler summary="median">

http://codeforces.com/contest/713/problem/C 7

http://www.spoj.com/problems/RMID2/ 4

http://www.spoj.com/problems/RMID/ 3 (as above just not so dynamic)

http://www.spoj.com/problems/EC_ESTA/ 4 //classical dynamic median

http://www.spoj.com/problems/DCEPCA09/ (6) //VERY NICE [MO +++ MEDIAN, MEAN, FREQ]

</spoiler>

<spoiler summary="meet_in_middle">

https://codeforces.com/gym/102307/problem/H (6) //[VERY NICE][RECURSION][BS]

http://codeforces.com/contest/912/problem/E (5) //[VERY NICE][BS][2P][PRIMES]

http://codeforces.com/contest/888/problem/E (4) //NICE[EASY]

http://codeforces.com/contest/51/problem/E (6) //NICE[GRAPH][Cycles of length 5]

https://devskill.com/CodingProblems/ViewProblem/245

https://devskill.com/CodingProblems/ViewProblem/256

11851 UVA (5)

11465 UVA (5)

13207 UVA (4) //Straight-forward MIM

http://www.spoj.com/problems/COLOR_CC/ (4) //VERY NICE &mdash; div by partity (take lesser) → 8^6

</spoiler>

<spoiler summary="MO">

http://www.spoj.com/problems/ADAUNIQ/ [Updates]

http://www.spoj.com/problems/ADANUM/

http://www.spoj.com/problems/ADAPEAR/

http://www.spoj.com/problems/ADAPHONE/

https://www.spoj.com/problems/MOZHSLS/ (5) //[VERY NICE]

http://www.spoj.com/problems/ADAFTBLL/ [Tree][Updates]

http://codeforces.com/gym/101879/problem/H (5) //[NICE][CLASSICAL][FREQUENCIES][FENWICK][BS]

http://www.spoj.com/problems/FREQUENT/

http://codeforces.com/contest/86/problem/D (4) //[NICE][CLASSICAL]

http://codeforces.com/contest/877/problem/F (6) //[NICE][NORMALIZE]

http://codeforces.com/problemset/problem/687/D

http://codeforces.com/problemset/problem/617/E

http://www.spoj.com/problems/DCEPCA09/

http://www.spoj.com/problems/COT2/

https://www.codechef.com/problems/DISTNUM3 //Tree + Update

https://toph.ws/p/distinct-dishting //Not sure if still working??

https://www.codechef.com/problems/CHEFNUMK

https://www.hackerearth.com/problem/algorithm/harry-gets-into-infy-1/description/

http://www.spoj.com/problems/COT/ (7) //ON TREE [but very tight TLE]

http://www.spoj.com/problems/GOT/ (5) //ON TREE

http://www.spoj.com/problems/CPAIR2/ (4) //MO + Fenwick [VERY NICE]

http://www.spoj.com/problems/HRSIAM/ (5) //With updates

http://www.spoj.com/problems/KDOMINO/ (4) //NICE &mdash; Frequencies

</spoiler>

<spoiler summary="next">

https://codeforces.com/contest/1187/problem/B (3) //[NICE]

13257 - License Plates [UVA](3) //Brute-Force 26^3 queries in O(1)

http://codeforces.com/contest/92/problem/C (3) //[VERY NICE]

LightOJ	1157

https://www.codechef.com/problems/ASTRING

http://www.spoj.com/problems/MAIN8_E/

http://codeforces.com/problemset/problem/701/C

http://www.spoj.com/problems/STRSEQ/ //+DP

http://codeforces.com/problemset/problem/762/C

http://codeforces.com/problemset/problem/724/D

http://www.spoj.com/problems/SUBSN/ //+BS

https://www.hackerrank.com/contests/world-codesprint-5/challenges/short-palindrome //+DP

</spoiler>

<spoiler summary="np-hard">

http://www.spoj.com/problems/ADACROW

http://www.spoj.com/problems/ADAPARTY/

http://www.spoj.com/problems/ADAPARTI/

http://codeforces.com/gym/101908/problem/J (6) //[VERY NICE][STEINER][GEOMETRY]

http://codeforces.com/gym/101666 [G] (6) //[NICE][BURTE FORCE][OBSERVATION][SUBSETS]

http://codeforces.com/contest/907/problem/E (5) //[VERY NICE][CLIQUE][DP]

http://codeforces.com/contest/114/problem/B (3) //[CLIQUE][BRUTE-FORCE]

http://www.spoj.com/problems/JOHNNY/ //Not exact &mdash; points

http://www.spoj.com/problems/TAKIN/ (3) //[KNAPSACK][RECURSION]

http://codeforces.com/contest/839/problem/E (5) //NICE! Max-Clique

7743 - Cliques (Similar to ADAPARTI) (8) //Parametrisation

7616	Counting Cliques (4) //[NICE][CLIQUES][ELIMINATING-SETS]

</spoiler>

<spoiler summary="number_rectangle">

https://codeforces.com/contest/1181/problem/A (2) //[EASY][FORMULA][MODULO]

https://www.spoj.com/problems/PRADIPSUM/ (2) //[EASY][FORMULA]

UVA	10667 //Largest rectangle

UVA	10074 //Largest rectangle

UVA	836 //Largest rectangle

UVA	1330 //Largest rectangle

12192 UVA 5

http://codeforces.com/contest/729/problem/B 2

http://codeforces.com/contest/710/problem/C 4

11871 UVA 6

11617 UVA (3)

11573 UVA (4)

11499 UVA (5)

11230 UVA (4)

http://www.spoj.com/problems/JOCHEF/ (5) //NICE: Lagers rectange 0/1 O(N*M)

</spoiler>

<spoiler summary="number_theory">

http://www.spoj.com/problems/ADAGCD/ [+STL]

http://www.spoj.com/problems/ADAHACK/

http://www.spoj.com/problems/ADADUNG/

http://www.spoj.com/problems/ADACAROT/

http://www.spoj.com/problems/ADACON/

http://www.spoj.com/problems/ADATAXES/

http://www.spoj.com/problems/ADADIG/

http://www.spoj.com/problems/ADASETS/

https://codeforces.com/gym/102302/problem/G (8) //[OBSERVE][EASY IMPLE]

https://codeforces.com/contest/1206/problem/B (2) //[IMPLE][IF]

https://codeforces.com/contest/1177/problem/B (4) //[NICE][LOGARITHM]

https://codeforces.com/contest/1148/problem/G (6) //[VERY NICE][RANDOM][FACTORISATION][GCD][PRIME]

https://codeforces.com/contest/1175/problem/A (2) //[EASY][SYMPATHIC][DIVISION]

https://codeforces.com/contest/1203/problem/C (3) //[NICE][GCD]

https://devskill.com/CodingProblems/ViewProblem/553 (3) //[VERY NICE][SIMPLE]

https://devskill.com/CodingProblems/ViewProblem/560 (2)

https://codeforces.com/contest/1176/problem/B (2) //[MODULO][GREEDY]

https://codeforces.com/contest/1200/problem/C (4) //[VERY NICE][GCD][LCM]

https://codeforces.com/contest/1182/problem/A (2) //[EASY][DP]

https://atcoder.jp/contests/abc136/tasks/abc136_b (2) //[IMPLEMENTATION][CONVERSION]

https://codeforces.com/contest/1185/problem/A (1)

https://codeforces.com/contest/1198/problem/F (6) //[VERY NICE][RANDOM][FACTORISATION][PRIME][GCD]

https://codeforces.com/contest/1183/problem/B (2) //[EASY][FORMULA][MIN/MAX]

https://codeforces.com/contest/1187/problem/A (1) //[EASY][FORMULA]

https://codeforces.com/contest/1195/problem/B (2) //[EASY][GAUSS][BRUTE]

https://codeforces.com/contest/1189/problem/E (5) //[INVERSION][STL]

https://www.spoj.com/problems/CANPR/ (5) //[NICE][MOBIUS] Weird TC (weak?)

https://www.spoj.com/problems/OVISLARSUM/ (3) //[FORMULA][128]

https://www.urionlinejudge.com.br/judge/en/problems/view/2876 (6) //[VERY NICE][GCD][IE]

https://codeforces.com/gym/102058/problem/E (3) //[BRUTE-FORCE][GCD]

https://codeforces.com/gym/101972/problem/A (3) //[EASY][SIMULATION]

https://toph.co/p/pascals-triangle (2)

https://toph.co/p/big-factorials (1)

https://www.codechef.com/viewsolution/21428053 (4) //[SORTING][ANGLES][MATH][COSINUS]

http://codeforces.com/gym/101962 [C] (4)

http://codeforces.com/gym/101808/problem/G (4) //[GCD][IF][LCM]

http://codeforces.com/gym/101666 [L] (5) //[GREED][DP] Logarithms

http://codeforces.com/gym/101666 [C] (4) //[NICE][GCD]

13287 - Shattered Cake (2) //Rectangle

http://codeforces.com/gym/101650 [G](3) //Graphs

http://codeforces.com/contest/934/problem/D (4) //Polynomials

8253 - Boss Battle [LA] (2)

http://codeforces.com/contest/919/problem/E (5) //[MODULAR-MATH]

http://codeforces.com/contest/149/problem/B (3) //Base to 10

http://codeforces.com/contest/148/problem/B (3) //[SIMULATION](math or bs)

http://codeforces.com/contest/148/problem/A (2) //[EASY][SIEVE][BRUTE-FOCE][LCM][IE]

http://www.spoj.com/problems/JGTLE/ (3) //Sum reduction

http://www.spoj.com/problems/BAPM/ (3) //Simple power / Observe, rare colisions

http://codeforces.com/contest/911/problem/C (2) //[Observation][Iff (or brute-froce)]

http://codeforces.com/contest/133/problem/B (2) //Bases + implementation

http://codeforces.com/contest/129/problem/A (1) //Parity

http://codeforces.com/contest/124/problem/D (4)

http://codeforces.com/contest/125/problem/A (1) //mod/div simple - if

http://codeforces.com/contest/902/problem/D (4) //Polynomials / Fibonacci / Bitset

http://codeforces.com/contest/899/problem/D (4) //X99999 possibilities

http://codeforces.com/contest/899/problem/C (3) //[NICE][GREEDY KNAPSACK]

http://codeforces.com/contest/899/problem/A (1)

http://codeforces.com/contest/898/problem/A (1)

http://codeforces.com/gym/101620 {F}(4) //[IFS][INVERSE][CASES]

http://codeforces.com/contest/900/problem/D (4) //[NICE][DIVISORS][GCD][IE]

http://codeforces.com/contest/900/problem/B (2) //Cycles or Brute-force + Division

http://codeforces.com/contest/119/problem/A (2) //[EASY][GCD]

8014 - Birthday Pizza Party (4) //[NICE][OVERFLOW][LCM WITH SHIFT]

7629 - Powers (3) //One path is factorisation

8037 - Military Service (2) //Sample formula

8085 - Divisors (4) //[NICE][PRIMES/FACTORISATION/SIEVE]

6589 - Captain Obvious and the Rabbit-Man (7) //Sylvester's formula

6582 - Magical GCD (4) //[NICE] - Data structures works too

8000 - FizzBuzz (1)

https://devskill.com/CodingProblems/ViewProblem/421 (2) //6 buckets

http://codeforces.com/contest/93/problem/E (5) //[VERY NICE][DP][RECURSION]

http://codeforces.com/contest/86/problem/A (3) //[NICE] 50* is best (unless more digits)

http://codeforces.com/contest/83/problem/D (5) //[VERY NICE][PRIMES][BRUTE-FORE-2]

http://codeforces.com/contest/82/problem/A (2) //Simulation

http://codeforces.com/contest/74/problem/C (4) //gcd

http://codeforces.com/contest/76/problem/E (4) //Divide sumations [BF]

http://codeforces.com/contest/71/problem/C (3) //[EASY][NICE][BRUTE-FORCE][DIVISORS]

http://codeforces.com/contest/70/problem/A (2) //3^(N-1)

http://codeforces.com/contest/43/problem/C (2) //Moduly by 3 {0/2+min(1,2)}

http://codeforces.com/contest/50/problem/A (1) //[EASY]

http://codeforces.com/contest/61/problem/C (4) //Base conversion + roman

UVA	355 //bases conversion

2559 [LA] //Base conversion

https://www.codechef.com/problems/COPRIME3 //Cyka Möbius

http://www.spoj.com/problems/PSTR/ //Cyka Möbius

http://codeforces.com/problemset/problem/803/F //Cyka Möbius

https://devskill.com/CodingProblems/ViewProblem/23

http://codeforces.com/contest/731/problem/F 4

12031 UVA (8)

http://codeforces.com/contest/722/problem/F (8)

http://codeforces.com/contest/716/problem/C 4

http://codeforces.com/contest/711/problem/E (8)

http://codeforces.com/contest/710/problem/D (6)

13154 (UVA) 7

13166 (UVA) 5

11962 (UVA) 2

11718 UVA 3

11510 UVA (5)

11538 UVA (3) //good one &mdash; just math

11556 UVA (1)

http://codeforces.com/contest/757/problem/E (8)

http://codeforces.com/contest/758/problem/F (7)

11481 UVA (4)

11237 UVA (4) //Nice &mdash; seems like knapsbag but it it not

11155 UVA (4) //Almost as previous problem

11038 UVA (3) //counting digits on interval

http://codeforces.com/contest/763/problem/C (7)

11087 UVA (4) //Sums of two numbers divisible with <=500 (10^5)

http://codeforces.com/contest/678/problem/C 2 //LCM

http://codeforces.com/problemset/problem/665/F (8) //p^3 | p*q

http://www.spoj.com/problems/LCMSUM/ //Vzorec v knihovničce

http://www.spoj.com/problems/FRNDZND/ (2) // (size 1 == 1, else 0)

http://www.spoj.com/problems/EXPOR/ //bit-by-bit (+ formula)

http://www.spoj.com/problems/FACTDIV/ (5) //dyn-update of ans/factors GOOD

http://www.spoj.com/problems/PAIRDIV/ (6) //cyka möbius -_-

http://www.spoj.com/problems/FCDC/ (4) //keep factorized factorial

http://www.spoj.com/problems/NTHPRIME/ (7) // BS + NumPrime GOOD!!

http://www.spoj.com/problems/DIVFACT3/ (7) // Sieve 10^8 + sqrt search

http://www.spoj.com/problems/DIVFACT4/ (8) // Prime count

http://codeforces.com/contest/776/problem/C (4) //segments div. by number

http://codeforces.com/contest/776/problem/E (6) //vypsat cisla: f(N)=Phi(N),g(N)=N

http://www.spoj.com/problems/PHT/ (2) //easy BS (NN+2N) mby math?

http://www.spoj.com/problems/GCDEX/ (7) //OEIS A006579  &mdash; enough [well imp]

http://www.spoj.com/problems/APS/ (3) //just sieve + generate

http://www.spoj.com/problems/WPC5I/ (3)//fc: C[a]!=C[b]:F[a]^max(C[a],C[b])

http://www.spoj.com/problems/SPEC_SET/ N→N/k→N/k/k

http://www.spoj.com/problems/DCEPC11B/ (5) //Wilson't theorem!

http://www.spoj.com/problems/FACTMULN/ (5) //each f[i]/c[i] separately

http://www.spoj.com/problems/SPCM/ (4) //just factorisation + prime check (10^12)

http://www.spoj.com/problems/TWOGAME/ (5) //gcd == Power of 3 => YES

http://www.spoj.com/problems/MKEQUAL/ (2) //Chceck if sum is divisible by N

http://www.spoj.com/problems/TIPTOP/ (3) //sqrt(N)==N? NICE!!

http://www.spoj.com/problems/PSYCHON/ (4) // fast factorisation

http://www.spoj.com/problems/ENIGMATH/ (1) // swap and div by gcd

http://www.spoj.com/problems/SNGPG/ (3) // prime gen + check

http://codeforces.com/contest/795/problem/A (2) //brute-force

http://codeforces.com/contest/801/problem/E (6) //NICE! &mdash; Clique-DAG + inversion

http://codeforces.com/contest/798/problem/C (4) //GCD == at the beginning OR 2

http://codeforces.com/contest/803/problem/C (3) //Only "low" K and just divisors

10830 (4) //simple add 2→ sqrt(N) + their mirrors

http://codeforces.com/contest/817/problem/A (2) //check division + parity

13209 UVA (3) //Simple simulation of division (+states rememberance)

http://codeforces.com/contest/834/problem/C (4) //Has cube-root + both num divisible by cuberoot

http://codeforces.com/contest/837/problem/E (5) //Factorisation + GCD attributes

http://www.spoj.com/problems/SUMMATION/ (3) //Number contribution: 2^(N-1)

http://www.spoj.com/problems/SECTORS/ (4) //Odd len OR sum of odd indices == sum of even

http://www.spoj.com/problems/IITKWPCM/ (6) //VERY NICE &mdash; Gauss's generalisation of Wilsons Theorem

http://www.spoj.com/problems/UCV2013A/ (4) //N*(N^L-1)/(N-1)

http://www.spoj.com/problems/KIMO1/ (4) //NICE &mdash; Adding/Subing by modulus

http://www.spoj.com/problems/AFS2/ (4) //Sum of divisort (sqrt(N)) &mdash; (+128int)

http://www.spoj.com/problems/FUNNUMS/ (4) //Permutations (get ith + guess ith)

http://www.spoj.com/problems/MAY99_3/ (3) //GCD

http://www.spoj.com/problems/PUCMM334/ (3) //Classical hats problem

http://www.spoj.com/problems/LCPC11B/ (4) //Factorize + count all subsets

http://www.spoj.com/problems/THREENUMBERS/ (2) //EASY & NICE [lcm]

http://www.spoj.com/problems/GAMES/ (2) //EASY&NICE &mdash; Go discrete (by 10^k) → 10^k/GCD

http://www.spoj.com/problems/SUBSHARD/ (4) //dig*10^sufix*(choose sufix)*^Prefix [VERY NICE]

http://www.spoj.com/problems/INVDIV/ (6) //Sum of divisors function + factorisation [NICE]

http://www.spoj.com/problems/JNEXT/ (2) //EASY &mdash; Zahřívačka pro prváky

http://www.spoj.com/problems/TSHOW1/ (3) //NICE &mdash; Almost as binary repre with 5/6

http://codeforces.com/contest/859/problem/B (2) //Easy by iteration

http://codeforces.com/contest/861/problem/A (2) //5,2 division [EASY]

http://www.spoj.com/problems/ABA12D/ (4) //NICE &mdash; Formula for sum divisors Prod(Sum(fac-powers))

http://www.spoj.com/problems/MAIN74/ (3) //Fibo's

http://www.spoj.com/problems/NOSQ/ (3) //Sieve + Digit check

http://www.spoj.com/problems/SQUAREV1/ (3) //NICE (but dumb code limit)

http://codeforces.com/contest/597/problem/A (1) //Simple if+2*Divide

http://www.spoj.com/problems/STREETR/ (3) //Easy [GCD]

http://www.spoj.com/problems/HPYNOSII/ (3) //<=1000 after first move

http://www.spoj.com/problems/HPYNOS/ (1) //Same as above &mdash; 1 number

http://www.spoj.com/problems/IITD4/ (3) //Brute-force [sieve-like]

http://www.spoj.com/problems/GIRLSNBS/ (2) //Some easy formula

http://www.spoj.com/problems/GUESSTHE/ (2) //NICE [EASY][LCM]

http://codeforces.com/contest/867/problem/B (2) //NICE [observation][1 2]

http://www.spoj.com/problems/NDIVPHI/ (4) //NICE &mdash; Multiple of lowest primes [BIG-INT]

http://www.spoj.com/problems/NDIVPHI2/ (5) //NICE &mdash; Same as above [bigger constraints]

http://codeforces.com/contest/6/problem/A (1) //Triangle check (4 pts)

http://codeforces.com/contest/869/problem/B (1) //Answer is usually 0

http://codeforces.com/contest/9/problem/C (2) //Bases (2→ 10)

http://codeforces.com/contest/20/problem/B (2) //Ax^2+Bx+C=0 (find roots)

http://codeforces.com/contest/27/problem/E (5) //[VERY NICE]: Factorisation+Recursion

http://codeforces.com/contest/32/problem/C (3) //DSU works too

http://codeforces.com/contest/872/problem/C (3) //NICE &mdash; Compose of 4 (mby one  6 or 9)

http://codeforces.com/contest/876/problem/B (3) //Group by modulo

</spoiler>

<spoiler summary="observation">

http://www.spoj.com/problems/ADABANKET/ //Observation (but Stoer-Wagner works too)

https://codeforces.com/gym/102302/problem/C (5) //[NICE][STL][BF]

https://codeforces.com/gym/102307/problem/K (4) //[NICE][FIBO][NUMBER THEORY]

https://codeforces.com/contest/1206/problem/D (5) //[VERY NICE][PARAMETRISATION][REDUCTION][BFS]

https://codeforces.com/contest/1204/problem/D1 (4) //[or DP][FIXED][GREEDY][STACK]

https://codeforces.com/contest/1204/problem/D2 (5) // ^^^

https://codeforces.com/contest/1194/problem/A (1) //[TRIVIAL]

https://www.spoj.com/problems/ARRTWIST/ (3)

https://www.spoj.com/problems/OPMODULO/ (3) //[NICE]Brute-force and observe

https://codeforces.com/gym/102001/problem/I (2) //[PARITY]

https://codeforces.com/gym/102001/problem/A (4) //[VERY NICE][FREQUENCY]

https://codeforces.com/gym/101991/problem/L (3) //[NICE][EASY][BITS]

https://codeforces.com/gym/102021 [F] (3) //[NICE][SEQENCE]

https://www.codechef.com/problems/BUDDYNIM (3) //[OBSERVATION][NICE]

http://codeforces.com/gym/101962/problem/H (4) //[SEQUENCES][SIMULATION]

http://codeforces.com/contest/922/problem/C (3) //Note that K is always very low

http://codeforces.com/contest/912/problem/B (2) //Bits/XOR

http://codeforces.com/contest/911/problem/D (3) //[VERY NICE]

http://codeforces.com/contest/902/problem/E (5) //[VERY NICE] //LCT works too

7589	Rearranging a Sequence (3) //Print from back and then real

http://codeforces.com/gym/101630 {A}(6) //[NICE][STL]

http://codeforces.com/contest/122/problem/B (1) //just 4 or 7

http://codeforces.com/contest/116/problem/E (6) //[NICE][COMBINATORICS][FIND ANY]

http://codeforces.com/contest/892/problem/D (4) //NICE [SORTING]

http://codeforces.com/contest/897/problem/E (5) //[NICE][SET] //2 will beat all

7730 To begin or not to begin (3) //Parity

http://codeforces.com/contest/122/problem/D (4) //[NICE] Sweep /OR/ cycle

http://codeforces.com/contest/128/problem/D (6) //Normalize + Sweeps

</spoiler>

<spoiler summary="oeis">

https://codeforces.com/gym/101981 [G] (3) //A000332

https://codeforces.com/gym/102001/problem/C //De Bruine

6591 - Bus (2) //2^N-1

12004 UVA 2

11273 UVA 5 //https://oeis.org/A001088

11077 UVA 3 //https://oeis.org/A094638

http://www.spoj.com/problems/VECTAR5/ 3 //https://oeis.org/A038721

http://www.spoj.com/problems/ESYRCRTN/ 2 //generate and see

http://www.spoj.com/problems/IITWPC4B/ 3 //http://oeis.org/A005044

http://www.spoj.com/problems/POLCONST/ (4) //A003401+Fermat Number (Prime)

http://www.spoj.com/problems/CUTCAKE/ (3) // pattern [1 22 333 4444 55555]

10872 UVA 3 //Alcuin's Sequence

http://www.spoj.com/problems/LOVINGPW/ (3) //A000788

http://www.spoj.com/problems/CBANK/ (3) //A000292 Tetrahedral numbers

http://www.spoj.com/problems/GUMATH2/ (4) //A000240 Modulo by MOD*2

http://www.spoj.com/problems/MATHII/ (4) //A006218  (Two formulas => sqrt(N))

http://www.spoj.com/problems/KOPC12B/ (4) //A002457 (factorial + factorial modular)

http://www.spoj.com/problems/YUMMY/ (4) //A006534

http://www.spoj.com/problems/ADV04B1/ (5) //A001850

http://www.spoj.com/problems/FLWRS/ (4) //A002464

http://www.spoj.com/problems/RANJAN02/ (3) //A024023

http://www.spoj.com/problems/BOMARBLE/ (2) //A000326

http://codeforces.com/contest/57/problem/C (4) //A045992

http://codeforces.com/contest/918/problem/A (1) //Fibo

</spoiler>

<spoiler summary="offline">

http://www.spoj.com/problems/ADARAIN/

http://www.spoj.com/problems/ADARAINB/

http://www.spoj.com/problems/ADAROBOT/

https://codeforces.com/gym/102307/problem/D (4) //[NICE][PREPROCESS][SQRT][DSU]

https://www.spoj.com/problems/CLFLARR/ (3) //[NICE][EASY][QUEUE][STL]

https://codeforces.com/gym/102021 [M] (5) //[VERY NICE][SPANNING]//LCA WORKS TOO

http://codeforces.com/gym/101840 [I] (4) //[NICE][PREPROCESS]

http://codeforces.com/problemset/problem/816/B //Easier ST

11266 UVA (6) //slightly knapsack || [NICE]

http://codeforces.com/contest/761/problem/F (7)

http://www.spoj.com/problems/UPDATEIT/ (2) //basic method

13189 UVA (4) //simulation + sort queries

http://www.spoj.com/problems/HAYBALE/ (3) //Basic sum + sort (segment tree would work too)

http://codeforces.com/gym/101597/problem/H (6) //Offline 2D sum + geometry

</spoiler>

<spoiler summary="palindromes">

https://codeforces.com/gym/102307/problem/B (3) //[BF][SUFFIX]

https://www.spoj.com/problems/JUSTAPAL/ (6) //[VERY NICE][SA][RMQ]

https://www.spoj.com/problems/DRAGKING/ (4) //[CLASSICAL][DP]

https://codeforces.com/gym/101981 (5) //[NICE][SEGMENT][MANACHER][ZETA][SA]

https://codeforces.com/gym/101972/problem/F (3) //[EASY][OBSERVATION][GREEDY]

http://codeforces.com/gym/101628/problem/E (4) //[NICE][DP] //Easy

http://codeforces.com/gym/101864 [J] (5) //[NICE][MANACHER]

http://codeforces.com/gym/101806/problem/Q (4) //[HASHING][PALINDROMIC-TREE]

http://codeforces.com/contest/897/problem/B (2) //Palindromic numbers [EASY][FIRST]

http://codeforces.com/contest/883/problem/H (3) //Make as least odd as possible

http://code-festival-2017-qualc.contest.atcoder.jp/tasks/code_festival_2017_qualc_c (3) //Similar to remove-dp, but greedy

http://code-festival-2017-qualc.contest.atcoder.jp/tasks/code_festival_2017_qualc_d (4) //DP with greedy thinking

http://codeforces.com/contest/59/problem/C (3) //Implementation [constructive]

UVA	13092 //manacher

http://www.spoj.com/problems/MSUBSTR/ //manacher

UVA	11888 //manacher

https://www.hackerrank.com/contests/101hack35/challenges/circular-palindromes //manacher

UVA	12378 //manacher

https://www.hackerrank.com/contests/world-codesprint-5/challenges/challenging-palindromes //SA

http://www.spoj.com/problems/NUMOFPAL/ //Palindromic Tree

http://codeforces.com/problemset/problem/245/H //# of palindromes [DP]

http://www.spoj.com/problems/ANAGR/ 2 //frequency + palindromes

http://www.spoj.com/problems/AMR12D/ (1) //Palindrome check //Zahrivacka pro prvaky

http://codeforces.com/problemset/problem/835/D //Hashing

http://codeforces.com/contest/137/problem/D (4) //[NICE][DP]

</spoiler>

<spoiler summary="patter-matching">

11019 UVA (5)

</spoiler>

<spoiler summary="permutations">

http://codeforces.com/contest/137/problem/B (1) //Frequency + size

http://codeforces.com/contest/136/problem/A (1) //Permutation cycles

http://codeforces.com/contest/844/problem/C 3 //NICE Permutations in array

http://codeforces.com/contest/48/problem/D (3) //NICE [frequency array]

http://codeforces.com/contest/56/problem/B (2) //Restore from 1 reverse [EASY]

http://codeforces.com/contest/122/problem/D (5) //NICE [BRUTE-FORCE]//ONLY BACK MATTERS

</spoiler>

<spoiler summary="persistent_segment_tree">

http://codeforces.com/contest/893/problem/F (6) //[VERY NICE][EULER TOUR]

http://codeforces.com/contest/813/problem/E (6) //Easy but hard data structure

https://codeforces.com/contest/893/problem/F //Suggested by [user:phibrain]

</spoiler>

<spoiler summary="preprocess">

http://www.spoj.com/problems/ADAPLUS/

https://codeforces.com/contest/1169/problem/E (5) //[VERY NICE][DP][NEXT][BITS]

https://codeforces.com/contest/1175/problem/E (5) //[VERY NICE][LIFTING][PRIORITY]

https://codeforces.com/contest/1181/problem/C (4) //[VERY NICE][RMQ]

https://atcoder.jp/contests/abc136/tasks/abc136_d (4) //[NICE][PARITY]

https://codeforces.com/contest/1194/problem/B (3) //[IMPLEMENTATION][INDEXING]

http://www.spoj.com/problems/ADASQR/ [Monotone Queue]

https://toph.co/p/rio-and-inversion (5) //[NICE][INVERSIONS][PREFIX SUM][2D]

http://codeforces.com/gym/101801 [I] (3) //[PREFIX SUM]

http://codeforces.com/gym/101889 [L] (5) //[NICE][PREFIX SUM][BINARY SEARCH]

http://codeforces.com/contest/120/problem/D (3) //But maybe work naively ?!

http://codeforces.com/contest/48/problem/B (2) //2D Prefix Sum [BF prolly works too]

http://codeforces.com/problemset/problem/761/F

VA	10360 //2D Prefix Sum

UVA	983 //2D Prefix Sum

http://codeforces.com/contest/777/problem/C (4) //NICE

http://codeforces.com/contest/818/problem/C (4) //Prefix Sum

http://codeforces.com/contest/834/problem/B (2) //26 queries &mdash; NICE rozehrivacka pro prvaky

http://www.spoj.com/problems/RANGESUM/ (4) //NICE: Offline (delta) + Prefix Sum

http://www.spoj.com/problems/RANDG/ (3) //NICE [but too low bounds] [PrefixSum] [Try all indexes]

http://www.spoj.com/problems/HARSHAD/ (3) //Sieve + simple function

http://www.spoj.com/problems/PUCMM210/ (3) //Number theory (thinking not necessary)

http://www.spoj.com/problems/BCAKE/ (3) //Prefix sum of rectangle + N^4

http://www.spoj.com/problems/PAIRSUM/ (4) //VERY NICE &mdash; Prefix sum + Prefix PW sum

http://www.spoj.com/problems/MAIN111/ (3) //Sieve + Brute Force (answer in O(1))

http://www.spoj.com/problems/PLUSEVI/ (4) //NICE &mdash; There are not many of them

http://codeforces.com/contest/18/problem/C (2) //Prefix sum End==2*i

http://codeforces.com/contest/873/problem/B (2) //Search for same prefix (+/-1)

http://codeforces.com/contest/33/problem/C (4) //Prefix sum + Sweep from back + sweep from front

http://codeforces.com/contest/872/problem/B (3) //Sweep from both sides (RMQ works too)

</spoiler>

<spoiler summary="prime-count">

http://www.spoj.com/problems/NTHPRIME/

http://www.spoj.com/problems/DIVFACT4/

http://codeforces.com/problemset/problem/665/F

https://www.codechef.com/problems/CNTPRIME

http://www.spoj.com/problems/SUMPRIM1/

http://www.spoj.com/problems/SUMPRIM2/ [NO &mdash; hard]

https://www.hackerrank.com/contests/projecteuler/challenges/euler010/problem //easy

</spoiler>

<spoiler summary="prime-testing">

http://www.spoj.com/problems/ADAGIFT/

https://codeforces.com/gym/102302/problem/J (5) //[NICE][NUMBER THEORY][SORTING]

https://www.spoj.com/problems/PRMFN/ (5) //[VERY NICE][GREEDY]

http://www.spoj.com/problems/PON/en/

http://www.spoj.com/problems/DAYOUT2C/en/ [EASY]

Project Euler #60: Prime pair sets

Project Euler #58: Spiral primes

Project Euler #131: Prime cube partnership

https://devskill.com/CodingProblems/ViewProblem/229

https://devskill.com/CodingProblems/ViewProblem/327

Gym	100753K [2015 German Collegiate Programming Contest (GCPC 15) + POI 10-T3]

Project Euler #130: Composites with prime repunit property

http://www.spoj.com/problems/ABA12A/ (3)

10871 UVA (3) //Easy &mdash; fermat not necessary

http://www.spoj.com/problems/POP1/ (4) //Fast primality testing (or somehow)

http://www.spoj.com/problems/POP2/ (5) //NICE &mdash; same as above (yet with ll)

http://www.spoj.com/problems/POP3/ (6) //same as above (yet with big)

http://www.spoj.com/problems/DCEPC203/ (6) //NICE [optimalisation]

http://www.spoj.com/problems/PRIMPERM/ (4) //NICE (next_perm + sieve)

</spoiler>

<spoiler summary="probability">

https://codeforces.com/gym/102302/problem/F (4) //[PATTERN]

https://codeforces.com/contest/1173/problem/E1 (5) //[NICE][DP]

https://codeforces.com/contest/1194/problem/F (6) //[NICE][COMBINATORICS][PREPROCESS]

http://codeforces.com/gym/101982 (5) [K] (5) //[NICE][DP]

http://codeforces.com/gym/101845/problem/G (4) //[DP] Classical

http://codeforces.com/gym/101845/problem/M (3) //[NICE][OBSERVATION]

http://codeforces.com/gym/101726/problem/B (4) //[NICE][DP][BRUTE-FORCE]

https://www.devskill.com/CodingProblems/ViewProblem/470 (3) //Brute Force

8262 - Knockout Tournament (4) [LA] //[NICE][SIMULATION] //Might not be working on LA (but on CF y)

http://codeforces.com/contest/912/problem/D (4) //[VERY NICE][EXPECT][DIJKSTRA]

http://codeforces.com/contest/908/problem/D (5) //[DP][MATH][INVERSION]

7821 - Elections (4) //[EASY][DP]

http://codeforces.com/gym/101620 {G}(5) //[VERY NICE][DIJKSTRA][EXPECTED VALUE]

http://codeforces.com/contest/110/problem/D (4) //[NICE][COMBINATORICS]

http://codeforces.com/contest/108/problem/D (4) //[NICE][SIMPLE][COMBINATORICS]

7619 - Guessing the Dice Roll (5) //[NICE][AHO][MATRIX EXPO]

7998 - Election (3) //Math works too [probability][DP]

LightOJ	1104 //Birthday Paradox

Gym	101064K [2016 USP Try-outs] //Birthday Paradox

11762 UVA (5)

11427 UVA (5)

11348 UVA (2)

http://codeforces.com/contest/768/problem/D (4) //With DP

http://www.spoj.com/problems/IITWPC4J/ (4) //with DP

10828 UVA (5) //Nice problem but bad statemend: Expected value of visits MC

10777 UVA (4) //NICE &mdash; yet solvable with DP

http://codeforces.com/contest/839/problem/C (3) //NICE & Easy => Tree

http://www.spoj.com/problems/ZCR/ (3) //Easy (+DP)

http://www.spoj.com/problems/IITKWPCN/ (2) //Easy &mdash; Odd/Eve (black balls)

http://codeforces.com/contest/846/problem/F (5) // Expected number of unique elements

http://www.spoj.com/problems/BTCODE_H/ (4) //DP (but main GROW is idea)

http://codeforces.com/contest/867/problem/D (5) //VERY NICE [DP]

http://codeforces.com/contest/24/problem/D (5) //VERY NICE [DP]+[TIME]

http://codeforces.com/contest/28/problem/C (4) //VERY NICE [DP]

</spoiler>


<spoiler summary="recursion">

https://codeforces.com/contest/1175/problem/B (3) //[STACK]

https://www.codechef.com/problems/HPIRATES (4) //[VERY NICE][OBSERVATION][GRAPHS]

8255 - Dunglish [LA] (3) //Finding all possibilities

http://codeforces.com/contest/915/problem/C (4) //[NICE][DP-works-too][GREEDY]

http://codeforces.com/contest/134/problem/B (4) //Number Theory

http://codeforces.com/contest/897/problem/C (4) //+Slightly [DP]

6585 - Draughts (4) //[NICE][BACKTRACK][DFS]

http://codeforces.com/contest/68/problem/D (5) //[NICE] Keep max and kill branches

UVA	536 //Tree from dfs

UVA	12347 //BST from preorder

http://www.spoj.com/problems/GOC11A/ 4

13170 UVA (7) //heavy implementation &mdash; but NICE!

10854 UVA (3) //if/else

http://codeforces.com/contest/31/problem/D (4) //[NICE] Brute-force by recursion

http://codeforces.com/contest/36/problem/B (2) //[NICE][SIMPLE]

</spoiler>

<spoiler summary="RMQ">

https://www.spoj.com/problems/MOZPWS/ (4) //[NICE][IMPLEMENTATION][MQ]

https://codeforces.com/contest/1208/problem/E (5) //[VERY NICE][OFFLINE][ST]

https://codeforces.com/gym/101972/problem/G (4) //[NICE][SWEEP WORKS TOO]

http://codeforces.com/problemset/problem/514/D //+BS

http://codeforces.com/problemset/problem/872/B

http://www.spoj.com/problems/TNVFC1M/

https://devskill.com/CodingProblems/ViewProblem/19

http://codeforces.com/contest/713/problem/D 6

http://codeforces.com/contest/675/problem/E 5

http://www.spoj.com/problems/POSTERIN/ 5 //VERY NICE &mdash; Delete all minimas

http://www.spoj.com/problems/RPLN/ (3) //RMQ only

http://www.spoj.com/problems/CITY2/ (4) //RMQ + MAP [NICE][VAGUE STATEMENT]

http://www.spoj.com/problems/DIFERENC/ (4) //Solve separately (linear D&C)

http://codeforces.com/contest/863/problem/E (4) //OR some Queue / sorting

http://codeforces.com/contest/5/problem/C (4) //NICE &mdash; many other options

http://codeforces.com/contest/15/problem/D (5) //VERY NICE 2D RM  [sliding-windw][monotone-queue]

http://codeforces.com/contest/873/problem/E (5) //[NICE][Brute-Force + RMQ]

</spoiler>

<spoiler summary="rope">

http://www.spoj.com/problems/AROPE/ 4

http://www.spoj.com/problems/AROPE2/ 5 //same as above (+time)

</spoiler>

<spoiler summary="scc">

http://www.spoj.com/problems/ADAPANEL/ [combinatorics]

13301 - Impossible Communication (4) //[CUTE][SAMPLE][OBSERVATION][EASY]

http://codeforces.com/problemset/problem/427/C proposed by [user:unofficial10]

http://codeforces.com/contest/894/problem/E (5) //[NICE][DP]

https://devskill.com/CodingProblems/ViewProblem/79

UVA	11838

UVA	247

UVA	13057

UVA	12645

UVA	11770

UVA	12926

UVA	11324

UVA	11709

UVA	12745

http://www.spoj.com/problems/TFRIENDS/ (4) //just scc size

http://www.spoj.com/problems/CAPCITY/ (4) //scc destination [WEAK TC]

http://codeforces.com/contest/22/problem/E (5) //[NICE][make it strongly connected][SRC>DST]

</spoiler>

<spoiler summary="segment_tree">

http://www.spoj.com/problems/ADABERRY/ [+TREAP]

https://codeforces.com/gym/102307/problem/E (5) //[SWEEP]

https://codeforces.com/contest/1208/problem/D (5) //[NICE][GREEDY][BS]

https://codeforces.com/contest/1180/problem/E (6) //[VERY NICE]

https://codeforces.com/contest/1187/problem/D (5) //[VERY NICE][GREEDY][STACK]

https://toph.co/p/maintain-the-queue (5) //[NICE][QUEUE]

http://codeforces.com/gym/101992/problem/L (5) //[VERY NICE]

http://codeforces.com/gym/101982 [F] (6) //[SWEEP][NORMALIZE][NICE][XOR]

http://codeforces.com/gym/101962/problem/I (4) //[BS]

http://codeforces.com/gym/101801 [G] (5) //Two ST [SEQUENCE]

http://codeforces.com/gym/101879/problem/G (5) //Merge / Special

http://codeforces.com/gym/101741/problem/J (6) //[NICE][COMBINATORICS]

http://codeforces.com/contest/914/problem/D (5) //[NICE][GCD][LOG]

http://codeforces.com/contest/915/problem/E (5) //[VERY NICE][UNLIMITED]

http://codeforces.com/contest/145/problem/E (5) //[NICE]//Bit swap + subsequence

http://www.spoj.com/problems/ADAGF/

http://www.spoj.com/problems/ADATREE/

http://codeforces.com/contest/911/problem/G (7) //Segment tree over queries

http://codeforces.com/contest/895/problem/E (5) //[PRECISION]

http://codeforces.com/contest/52/problem/C (4) //Easy [MIN]+[INCREASE]

http://codeforces.com/contest/56/problem/E (5) //[NICE][NORMALIZE][MAX]

http://codeforces.com/contest/877/problem/E (5) //[VERY NICE][EULER TOUR TREE]

https://devskill.com/CodingProblems/ViewProblem/283

https://devskill.com/CodingProblems/ViewProblem/315

http://codeforces.com/problemset/problem/756/C

http://codeforces.com/contest/739/problem/C (8)

http://codeforces.com/contest/718/problem/C (8)

http://codeforces.com/contest/750/problem/E (7)

http://codeforces.com/contest/759/problem/C (7)

11165 UVA (5)

http://codeforces.com/contest/763/problem/E (8) //VERY NICE &mdash; [non-trivial]

http://www.spoj.com/problems/BGSHOOT/ (5) //normalize &mdash; then easy

http://www.spoj.com/problems/KGSS/ (4)

http://codeforces.com/contest/765/problem/F (7) //VERY NICE &mdash; CASCADE

http://www.spoj.com/problems/GSS1/ (5) //Idea &mdash; then easy

http://www.spoj.com/problems/KQUERYO/ (5) //Seg-tree of vectors

http://codeforces.com/contest/633/problem/G (8) //EulerTree+Seg+Bitset

http://www.spoj.com/problems/NAJ0001/ (7) //10^8 int &mdash; memory (and worked)

http://www.spoj.com/problems/PRMQUER/ (5) //2 segment trees + sieve

http://www.spoj.com/problems/EC_DIVS/ (5) //dunno if intended

http://www.spoj.com/problems/DCEPC11I/ (5) //NICE &mdash; 1,2,3,4,5,.. inc

http://www.spoj.com/problems/QUE2/ (4) //kth number

http://codeforces.com/contest/785/problem/E (6) //Seg+Treap [and faster]

http://codeforces.com/contest/786/problem/B (6) //+Dijkstra

13183 UVA (6) //Merge-Sort-Tree [dunno]

http://codeforces.com/contest/121/problem/E (7) //Dunno - done by vectorisation

http://codeforces.com/contest/803/problem/G (5) //VERY NICE!! &mdash; ST 10^9 + ST/RMQ 10^5

http://codeforces.com/contest/794/problem/F (7) //Digit by digit! (N*log(N)*100 ~passes,2017-10-19)

http://codeforces.com/contest/811/problem/E (6) //VERY NICE &mdash; DSU (easier Timofey + animals)

http://codeforces.com/contest/817/problem/F (7) //10^18 + MEX ~~ NICE yet problematic

http://codeforces.com/contest/816/problem/B (3) //Or offline trick makes it easier

http://codeforces.com/contest/834/problem/D (5) //+Dynamic Programming | NICE

http://www.spoj.com/problems/SBO/ (5) //preLast→ last (-1), last→ now (+1) &mdash; VERY NICE

http://www.spoj.com/problems/GOODE/ (5) //NICE: Inversion + L-Mex

http://www.spoj.com/problems/CNTPRIME/ (3) //ST+Sieve (short range)

http://www.spoj.com/problems/SEGSQRSS/ (4) //NICE {weak data} ~~ SQRT works too

http://www.spoj.com/problems/MON2012/ (5) //NICE [Online][10^9 Range]

http://www.spoj.com/problems/PARSUMS/ (4) //But other approaches work too

http://www.spoj.com/problems/THRBL/ (4) //Simple SA &mdash; maximum on range <= A[a]

http://www.spoj.com/problems/HORRIBLE/ (3) //Totally classical

http://www.spoj.com/problems/MULTQ3/ (4)  //NICE (interesting operation)

http://www.spoj.com/problems/PERMPATT/ (4) //NICE [minimum][+IDEA]

http://codeforces.com/contest/869/problem/E (5) //NICE &mdash; 2D [random][XOR]

http://codeforces.com/contest/19/problem/D (5) //NICE [+BS][+SET] {bs not necessary}

</spoiler>

<spoiler summary="sequences">

11885 UVA 7 //Previous problem requested for statement

11522 UVA 3 //Trick &mdash; low numbers only :P

https://codeforces.com/contest/1208/problem/A (2) //First few terms :)

</spoiler>

<spoiler summary="sieve">

http://www.spoj.com/problems/ADAPRIME/

https://devskill.com/CodingProblems/ViewProblem/577 (4) //[NICE][TWO POINTERS]

https://www.spoj.com/problems/EVENSEMIP/ (5) //[VERY NICE][SEGMENTED]

http://codeforces.com/gym/101982 [H] (3) //[GOLDBACH]

http://codeforces.com/contest/114/problem/E (5) //[NICE][FAST THINGS NEEDED][SEGMENTED]

http://codeforces.com/contest/58/problem/B (3) //[NICE][GREEDY][LEAST PRIME FACTOR]

Project Euler #134: Prime pair connection //Segmented

11610 UVA (5)

11353 UVA (3)

http://www.spoj.com/problems/TDPRIMES/ (4)

http://www.spoj.com/problems/VECTAR8/ (3)

http://www.spoj.com/problems/NFACTOR/ (4)

http://www.spoj.com/problems/HS08PAUL/ (4) //simply generate

http://codeforces.com/contest/776/problem/B (3) //Easy &mdash; trict: PM-1/ELSE-2

http://www.spoj.com/problems/GGD/ (4) // N/lowestDiv*(lowestDiv-1)

http://codeforces.com/contest/822/problem/D (4) //DP + Lowest factor

http://www.spoj.com/problems/NGIRL/ (4) //Squares &mdash; Primes + BS == Easiest

http://www.spoj.com/problems/PTRI/ (5) //Very fast sieve necessary:/

http://www.spoj.com/problems/AFS/ (3) //Sum of divisort + DP

http://www.spoj.com/problems/BSPRIME/ (4) //Very fast sieve needed

http://www.spoj.com/problems/DCEPC505/ (4) //NICE &mdash; at most 10527450

http://www.spoj.com/problems/CUBEFR/ (3) //NICE &mdash; Sieve out k^3 numbers

http://www.spoj.com/problems/PRIMES2/ (8) //VERY NICE &mdash; Some hell-shit optimizing

http://codeforces.com/contest/26/problem/A (2) //Easy &mdash; many ways to solve it

</spoiler>

<spoiler summary="simulation">

https://codeforces.com/contest/1169/problem/A (2) //Ifs shall work too

https://codeforces.com/contest/1180/problem/C (4) //[MODULO][QUEUE]

https://codeforces.com/gym/102001/problem/F (4) //[NICE][GREEDY]

https://codeforces.com/gym/101991/problem/D (4) //[NICE][NORMALIZE][PREFIX]

https://codeforces.com/gym/102021 [L] (5) //[NICE][JUST DO IT]

https://codeforces.com/gym/102021 [D] (4) //Try one and see

https://codeforces.com/gym/101972/problem/K (3) //[EASY][STRINGS]

http://codeforces.com/gym/101962/problem/K (3) //[NICE] //Complexity

http://codeforces.com/gym/101650 [A](7) //[VERY NICE][TREAP][PROBABILITY]

http://codeforces.com/gym/101650 [K](5) //[NICE] //Perhaps weak TC

https://abc084.contest.atcoder.jp/tasks/abc084_c (3) //Brute-Force

http://codeforces.com/contest/908/problem/B (2) //[EASY][NICE]

http://codeforces.com/contest/141/problem/B (3) //[NICE][IF-PARTY]

7921 - Anticlockwise Motion (4) //Simulate in sqrt

7691 - Falling Apples (3)

7977 - The Key to Cryptography (2)

http://codeforces.com/contest/129/problem/B (2) //Graph

http://codeforces.com/contest/903/problem/B (2) //[NICE]

http://codeforces.com/contest/120/problem/C (1)

http://codeforces.com/contest/118/problem/A (1)

8012 - Voting Fraud (1)

http://codeforces.com/contest/897/problem/A (1) //BF - do as they say

7985 - Bumper-to-Bumper Traffic (4) //FINE - We have whole time-lapse

7988	Flow Shop (3) //Do as they say. Trivial but not bad.

7703 - Reading Digits (2) //Simple simulate what they ask for

http://codeforces.com/contest/893/problem/A (1) //Easy but nice

http://codeforces.com/contest/102/problem/B (2) //Do as they write - log-convergence

http://codeforces.com/contest/92/problem/A (1) //Way too easy

http://codeforces.com/contest/88/problem/C (3) //[NUMBER THEORY]

http://codeforces.com/contest/84/problem/D (4) //Priority queue by min*size

http://codeforces.com/contest/79/problem/A (1) //Simulate rules

http://codeforces.com/contest/879/problem/A (1) //Iterate day-by-day

http://codeforces.com/contest/879/problem/B (3) //Either at most N^2 or the biggest element [NICE]

http://codeforces.com/contest/879/problem/D (4) //[NICE][Array elimination]

http://codeforces.com/contest/46/problem/A (2) //[EASY][MODULO]

http://codeforces.com/contest/46/problem/B (3) //[EASY][SEARCH-EACH-QUERY]

http://codeforces.com/contest/55/problem/A (2) //Simple (long) simulation

http://codeforces.com/contest/60/problem/A (1) //Moving LR bounds

12187 UVA (2)

http://codeforces.com/contest/724/problem/C 5

http://codeforces.com/contest/746/problem/C 3

11093 UVA (2)

http://codeforces.com/contest/768/problem/C (4)

http://www.spoj.com/problems/WRONG/ (5) //VERY NICE &mdash; precalculate from back, then go from front

http://codeforces.com/contest/864/problem/C (4) //Not nice &mdash; just iffs

http://www.spoj.com/problems/WAGE/ (3) //Simple Game Of Life Modification

http://codeforces.com/contest/6/problem/C (2) //Simple simulate from both sides

http://codeforces.com/contest/9/problem/B (2) //Simulate what is given (+ doubles)

http://codeforces.com/contest/11/problem/B (3) //sqrt(X) [diff must be even]

http://codeforces.com/contest/30/problem/A (2) //Simply simulate process [-1000→ 1000]

</spoiler>

<spoiler summary="sorting">

http://www.spoj.com/problems/ADATOMAT/

http://www.spoj.com/problems/ADAUSORT/

http://www.spoj.com/problems/ADACUT/

http://www.spoj.com/problems/ADAHLIA/

https://codeforces.com/contest/1148/problem/D (4) //[NICE][GREEDY]

https://codeforces.com/contest/1174/problem/B (3) //[OBSERVATION] Nice yet simple

https://codeforces.com/contest/1174/problem/A (2) //[EASY]

https://codeforces.com/contest/1203/problem/E (4) //[GREEDY][SIMPLE]

https://codeforces.com/contest/1203/problem/B (3) //[GREEDY][NICE]

https://codeforces.com/contest/1185/problem/D (4) //[BF][IMPLE][MATH]

https://codeforces.com/contest/1185/problem/C1 (3) //[GREEDY]

https://codeforces.com/contest/1197/problem/C (4) //[NICE][EASY][OBSERVATION]

https://codeforces.com/contest/1197/problem/A (3) //[SIMPLE][GREEDY][MATH]

https://codeforces.com/contest/1189/problem/B (3) //[EASY][OBSERVATION]

https://www.spoj.com/problems/SWAPDIFF1/ (4) //[CLASSICAL][INVERSIONS]

https://www.spoj.com/problems/SHINCARD/ (4) //[NICE]

https://www.spoj.com/problems/POTATOPL/ (4) //[NICE][GREEDY]

https://codeforces.com/gym/101991/problem/I (3)

http://codeforces.com/gym/101962/problem/M (4)

http://codeforces.com/gym/101726/problem/E (3) //[STRUCTURES][IMPLEMENTATION]

13282	Cakey McCakeFace (3) //Brute Force

8260	Installing Apps (4) //[NICE] //Sorting + some DP

http://codeforces.com/contest/922/problem/D (3) //[NICE][GREEDY][EASY]

http://codeforces.com/contest/920/problem/C (3) //[EASY] Sortable by parts

http://codeforces.com/contest/913/problem/D (4) //[NICE][BS][2P][FW]

http://codeforces.com/contest/149/problem/A (2) //Sorting|Greedy

http://www.spoj.com/problems/SEUG/ (2) //Bad statement

http://codeforces.com/contest/141/problem/A (2) //Or frequency

http://codeforces.com/contest/137/problem/E (4) //[NICE][PREFIX SUM MATCHING]

http://codeforces.com/contest/137/problem/C (4) //[NICE][FENWICK WORKS TOO]

http://codeforces.com/contest/136/problem/C (3) //Last to 1(2) |OR| first to INF

7601 - Football (3) //Greedy

7673 - What a Simple Research (2) //[EASY][IMPLE]

http://codeforces.com/contest/108/problem/B (2) //Easy & Adjacent

8025 - Stacking Cups (2)  //Sorting+input

http://codeforces.com/contest/892/problem/A (2) //[EASY][SUM]

https://www.urionlinejudge.com.br/judge/en/problems/view/2290 (3) //Sort+check [fast]

http://codeforces.com/contest/81/problem/C (3) //MATH[Lesser=greater][comparator]

http://codeforces.com/contest/53/problem/D (3) //Bubble sort

http://codeforces.com/contest/58/problem/D (4) //[BUCKET][GREEDY][STRING]

UVA	10810 //INV

UVA	11858 //INV

http://codeforces.com/problemset/problem/645/B //INV

UVA	10327 //INV

http://www.spoj.com/problems/BUBBLESORT/ //INV

UVA	11495 //INV [GAME]

http://www.spoj.com/problems/CODESPTB/ //INV

UVA	13212 //INV

http://codeforces.com/problemset/problem/749/E //INV

12189 UVA (3)

12196 UVA (4)

http://codeforces.com/contest/731/problem/D 7

11925 UVA (4)

11979 UVA (3)

http://codeforces.com/contest/747/problem/D (4)

11890 UVA (4)

http://www.spoj.com/problems/KAOS/ (4) //INV &mdash; GOOD problem!!!!

http://www.spoj.com/problems/KSMALL/ (5) //fast sort /or/ quick-select

http://www.spoj.com/problems/RKS/ (3) //use map

http://www.spoj.com/problems/SPCJ/ (4) //reverse + go from back

http://codeforces.com/contest/785/problem/B (2) //last-first + vice versa

http://codeforces.com/contest/798/problem/D (4) //Take 1st then take best B of every pair (sort by A)

http://codeforces.com/contest/810/problem/B (2)

http://codeforces.com/contest/810/problem/C (3) //+Math

http://codeforces.com/contest/814/problem/A (1) //Pro prváky &mdash; but nice observation

http://codeforces.com/contest/817/problem/B (3) //Frequency of TOP 3

10769 UVA (3) //Sadly N^4 passes

13208 UVA (4) //Sort + Prefix Sum

13212 UVA (3) //Number of inversions

http://codeforces.com/contest/831/problem/C (3) //NICE ~ Check all "add" against first

http://codeforces.com/contest/831/problem/D (4) //Can be solved with BS+Max-Match

http://codeforces.com/contest/841/problem/C (3) //NICE &mdash; match greatest to lowest

http://codeforces.com/contest/845/problem/C (2) //EASY &mdash; pro prvaky

http://www.spoj.com/problems/HSHW/ (4) //Test every big/low pair + big/big low/low on +/-

http://www.spoj.com/problems/CODESPTB/ (3) //Count inversions [BASIC]

http://codeforces.com/contest/863/problem/B (2) //Sort and omit 2

http://www.spoj.com/problems/AMR10G/ (2) //Easy yet NICE

http://codeforces.com/contest/12/problem/C (2) //Very simple

http://codeforces.com/contest/16/problem/B (1) //[EASY]

http://codeforces.com/contest/22/problem/D (3) //Sort by begin + sweep

http://codeforces.com/contest/23/problem/C (3) //Take them by pairs + add last

http://codeforces.com/contest/24/problem/B (3) //Simple follow the rules

http://codeforces.com/contest/27/problem/B (3) //Compare number of victories

http://codeforces.com/contest/27/problem/C (4) //[NICE] Find next bigger/lesser (sort)

</spoiler>

<spoiler summary="spanning_tree">

https://www.urionlinejudge.com.br/judge/en/problems/view/2683 (3) //[BASIC][MAXIMUM]

http://codeforces.com/contest/908/problem/F (5) //[VERY NICE] //Not exactly MST but similar[GREEDY]

http://codeforces.com/contest/125/problem/E (5) //[BS]

http://codeforces.com/contest/76/problem/A (4) //[VERY NICE] Sort by A and KEEP spanning + one edge

LA 6622 - Absurdistan Roads (4) //Plus one edge

UVA	12176

UVA	10600

UVA	10724

https://www.hackerrank.com/contests/june-world-codesprint/challenges/johnland

UVA	11710

Gym	101252C [2014-2015 CT S02E05: Codeforces Trainings Season 2 Episode 5 &mdash; 2009-2010 ACM-ICPC]

Gym	101047I [2015 USP Try-outs][HARD]

UVA	11183 [Directed]

LightOJ	1101

https://www.codechef.com/problems/CHEFELEC

UVA	10307

http://codeforces.com/problemset/problem/598/D

http://codeforces.com/problemset/problem/32/C

http://codeforces.com/problemset/problem/744/A

https://devskill.com/CodingProblems/ViewProblem/344

908 &mdash; Re-connecting Computer Sites [UVA]

1208 &mdash; Oreon [UVA]

1235 &mdash; Anti Brute Force Lock [UVA]

10034 &mdash; Freckles [UVA]

11228 &mdash; Transportation system [UVA]

11631 &mdash; Dark roads [UVA]

11733 &mdash; Airports [UVA]

11747 &mdash; Heavy Cycle Edges [UVA]

BLINNET SPOJ (3)

11183 UVA (4) //Directed [need to know algo!]

http://www.spoj.com/problems/ULM09/ (3) //Sum-Kruskal

http://www.spoj.com/problems/IITKWPCG/ (4) //VERY NICE [log instead of price]

http://codeforces.com/contest/17/problem/B (3) //Spanning tree [no dsu]

</spoiler>

<spoiler summary="spfa">

LightOJ	1074

UVA	1171

UVA	11478

UVA	12768

11478 UVA (5)

</spoiler>

<spoiler summary="sqrt">

https://codeforces.com/gym/102307/problem/J (5) //[NICE]

https://codeforces.com/contest/1207/problem/F (5) //[VERY NICE][MODULO][SIEVE-LIKE]

https://codeforces.com/contest/1199/problem/D (4) //[NICE][SIMPLE IMPLE]

https://www.spoj.com/problems/ZING01/ (5) //[VERY NICE][STRING][SEGMENT]

http://codeforces.com/gym/101889 [D] (6) //[NICE][STL]

http://codeforces.com/contest/916/problem/D (6) //[NICE][BS][BINARY-LIFTING]

12003 UVA 7

11990 UVA (5)

http://www.spoj.com/problems/GIVEAWAY/ (7) //SQRT + BS >  [or Seg+Trie]

http://codeforces.com/contest/786/problem/C (5) //Nsqrn (bg) + sqrSegs (end)

http://codeforces.com/contest/840/problem/D (5) //NICE &mdash; Either frequent OR brute-force

http://codeforces.com/contest/13/problem/E //VERY NICE [SQRT-BLOCK UPDATE/JUMP]

http://codeforces.com/contest/85/problem/D (4) //NICE [ST shall work too]

</spoiler>

<spoiler summary="stl">

http://www.spoj.com/problems/ADABASET/ [IO-testing][ARRAY]

http://www.spoj.com/problems/ADALIST/ [ROPE]

http://www.spoj.com/problems/ADAFIELD/ [SET]

http://www.spoj.com/problems/ADAQUEUE/

http://www.spoj.com/problems/ADAFRIEN/

https://codeforces.com/contest/1208/problem/B (3) //[NICE][TWO-POINTERS][BF]

https://www.spoj.com/problems/REDARR2/ (4) //[NICE][PQ]

https://www.spoj.com/problems/MINSTOCK/ (3) //[EASY][MAP]

http://codeforces.com/gym/101864 [F] (4) //[SET]

http://codeforces.com/contest/920/problem/B (3) //[NICE][QUEUE][SIMPLE]

http://codeforces.com/contest/911/problem/E (4) //[NICE][STACK][SET]

http://codeforces.com/contest/909/problem/D (4) //[VERY NICE][SIMULATION][GROUP]

http://codeforces.com/contest/899/problem/E (4) //[VERY NICE][SET]

https://arc087.contest.atcoder.jp/tasks/arc087_a (2) //Map

http://codeforces.com/contest/903/problem/C (2) //Map

http://codeforces.com/contest/900/problem/C (3) //[NICE][SET]

http://codeforces.com/contest/112/problem/A (1) //tolower [trivial]

3396 - Alphabetics (2) //Getline, letters identification

http://codeforces.com/contest/81/problem/A (2) //Stack OR string

http://codeforces.com/contest/78/problem/A (1) //fgets + imple

http://codeforces.com/contest/69/problem/E (3) //NICE [2POINTERS][SET][MAP]

http://www.spoj.com/problems/RMID/ //Dynamic Median

http://www.spoj.com/problems/RMID2/ //Dynamic Median

http://codeforces.com/problemset/problem/713/C //Dynamic Median

http://www.spoj.com/problems/EC_ESTA/ //Dynamic median

http://codeforces.com/contest/799/problem/B (2) //EASY &mdash; MAP

http://codeforces.com/contest/808/problem/D (3) //MAP

10887 (2) //string + map

10730 (3) //Easy with hash-map

http://codeforces.com/contest/821/problem/C (3) //STACK (vector) Nice+Easy

http://www.spoj.com/problems/SOLVEIT/ (3) //Set + lower_bound

http://www.spoj.com/problems/IITKWPCA/ (2) //Set + getline

http://codeforces.com/contest/849/problem/D (5) //Queue

http://www.spoj.com/problems/CRAN02/ (4) //Map (+Math)

http://www.spoj.com/problems/MAX_NUM/ (4) //Queue (possibly multiple ways)

http://www.spoj.com/problems/SID/ (5) //Sort + Vector (or similar) [strict TLE]

http://www.spoj.com/problems/RPLD/ (2) //Map of sets

http://codeforces.com/contest/861/problem/D (4) //unordered map of sets

http://www.spoj.com/problems/FACEFRND/ (2) //Set or Bitset

http://www.spoj.com/problems/HACKRNDM/ (3) //Easy &mdash; map

http://codeforces.com/contest/847/problem/K (4) //NICE Map+Queue

http://codeforces.com/contest/855/problem/A (1) //set

http://codeforces.com/contest/4/problem/C (2) //map+string

http://codeforces.com/contest/5/problem/E (6) //iffs + RMQ+BS+SET [or other sol]

http://codeforces.com/contest/44/problem/A (1) //Set + pair

http://codeforces.com/contest/45/problem/C (4) //NICE &mdash; Handling with sets

http://codeforces.com/contest/918/problem/B (2) //[MAP] //TLDR

</spoiler>

<spoiler summary="strings">

https://codeforces.com/contest/1189/problem/A (2) //[OBSERVATION]

https://codeforces.com/contest/1194/problem/C (3) //[EASY][FREQUENCY][2POINTERS]

https://www.spoj.com/problems/MAGSUB1/ (3) //[EASY][SYMPATHIC][COMBINATORICS]

https://www.urionlinejudge.com.br/judge/en/problems/view/2866 (1) //Reverse

https://codeforces.com/gym/101972/problem/H (3) //[NICE][PREPROCESS]

http://codeforces.com/contest/909/problem/A (1) //Lexicographical comparision [EASY]

7948	Periodic Strings (2) //Brute-force

7892 - Game of Matchings (6) //No idea - heuristic works - but seems to be nice

8017 - Mancunian and Sonu Generate Strings (5) //[NICE][DP]//+Something: Trie/SA/SET...?

http://codeforces.com/contest/890/problem/D (4) //[NICE][SET][SORTING][26][BRUTE-FORCE]

http://codeforces.com/contest/43/problem/B (2) //Frequency

http://codeforces.com/contest/50/problem/B (2) //Frequency + Power

http://www.spoj.com/problems/MINMOVE/ (3) //Minimal lexicographical rotation

http://www.spoj.com/problems/BWHEELER/ //Burrows Wheeler

http://www.spoj.com/problems/EDIST/ //Edit Distance

3189 LA //Edit Distance

https://www.hackerrank.com/contests/morgan-stanley-2015/challenges/minimum-transformation-cost/problem //Edit Distance

http://codeforces.com/gym/101492/problem/L //Laevenstein Distance

UVA	13068 //Lexicographically lowest rotation

2755 [LA]//Lexicographically lowest rotation

LightOJ	1073 //Lexicographically Shortest Superstring

http://codeforces.com/contest/762/problem/C 5

http://www.spoj.com/problems/LCS0/ 10 //LCS

http://www.spoj.com/problems/IITWPC4H/ 2 //Frequence array

13186 UVA (6)  //Bitset + Trie ~ NICE [6-7 mby?]

http://codeforces.com/contest/798/problem/B (2) //Brute-force .. pro prváky

10745 UVA (4) //Frequency (N^2 possible if efficient!!)

http://codeforces.com/contest/822/problem/B (2) //Easy pro prvaky (slightly imple.)

http://codeforces.com/contest/828/problem/C (4) //+Sorting (process only necessary!)

http://codeforces.com/contest/832/problem/B (3) //Naive compare back+front [+freq]

http://www.spoj.com/problems/STC04/ (5) //Next + pairs O(N*26) [frist look O(26^2*N)]

http://www.spoj.com/problems/IITKWPCJ/ (4) //GCD or HASHING

http://www.spoj.com/problems/SUBSN/ (4) //Next (NICE &mdash; bad input):

http://www.spoj.com/problems/BOGGLE/ (2) //EASY [MAP][STREAM]

http://www.spoj.com/problems/MAIN8_E/ (4) //VERY NICE &mdash; Next function

http://www.spoj.com/problems/STRMATCH/ (3) //Nice matching, yet low constraints on "N"

http://www.spoj.com/problems/FINDSR/ (3) //Clever bruteforce works here (NlogN)

http://codeforces.com/contest/39/problem/J (2) //Simple iteration over string

http://codeforces.com/contest/876/problem/E (4) //Compare from back + make fail-pairs

</spoiler>

<spoiler summary="suffix_array">

http://www.spoj.com/problems/ADAPHOTO/ [or hashing after turboanalisis]

http://www.spoj.com/problems/ADASTRNG/

https://codeforces.com/gym/102302/problem/K (7) //[VERY NICE][TREAP][TWO POINTERS]

https://codeforces.com/contest/1202/problem/E (5) //[NICE][OBSERVATION][RMQ]

https://codeforces.com/gym/101991/problem/E (6) //[VERY NICE][RMQ]Prolly an easier alternative

https://toph.co/p/distinctness (6) //[VERY NICE][SET][LCP][RMQ]

http://codeforces.com/gym/101889 [M] (6) //[VERY NICE][OBSERVATION]

http://codeforces.com/gym/101840 [B] (7) //[NICE][ST][BIT][LCP]

http://codeforces.com/contest/129/problem/D (4) //[NICE]//Suffix Automaton / Brute Force works too

http://codeforces.com/contest/123/problem/D (5) //[NICE][RMQ][D&C]

8086  Substring Sorting (7) //[VERY NICE][RMQ][BS][PST]

7702 - Castle //6 [VERY NICE][RMQ][BS][FW]

7701 - Favorite music //8 [VERY NICE][RMQ][SEARCH][OPTI] //WRONG TIME-LIMIT==OPTI

https://www.urionlinejudge.com.br/judge/en/problems/view/1530 //7 [VERY NICE][RMQ][SET][OFFLINE]

https://www.urionlinejudge.com.br/judge/en/problems/view/2000 (5) //Basic disubstr counting

UVA	760 //LCS

UVA	1227 //LCS

http://www.spoj.com/problems/LCS/en/  //LCS

UVA	11512

7502 [LA]

Gym	100923D [2015 ACM National Contest Romania &mdash; Round 1]

UVA	1254

UVA	12191

UVA	12206

https://www.codechef.com/problems/INSQ16F

3943 LA

UVA	11107

UVA	12974

UVA	10526

Davos and Reading [INSOMNIA] //Awesome problem but can't find link [hard] &mdash; non of regular judges

UVA	12338

https://devskill.com/CodingProblems/ViewProblem/328

12191 UVA 5

SARRAY SPOJ 3

4513 LA 6

http://www.spoj.com/problems/LCS2/ 7 // must be linear (SA+LCP+MQ)

http://codeforces.com/contest/802/problem/I 7 //NICE! SA+LCP+(Segmentree/queue)

http://www.spoj.com/problems/LONGCS/ //5 LCS  of multiple strings (NICE)

http://www.spoj.com/problems/SUBLEX/ //5 VERY NICE: Kth substring

http://codeforces.com/contest/873/problem/F //6 VERY NICE: SA+Histogram

http://codeforces.com/contest/30/problem/E //7 VERY NICE: [many other sols: Manach/KMP/HASH...]

6856 &mdash; Circle of digits //7 [VERY NICE]

</spoiler>


<spoiler summary="ternary_search">

LightOJ	1146

Gym	101482G [2014-2015 Northwestern European Regional Contest (NWERC 2014)]

Gym	101309D [2010-2011 ACM-ICPC Northeastern European Regional Contest (NEERC 10)]

UVA	13010 //+Dijkstra

2015-2016 CTU Open Contest: Chasing the Cheetah

12197 UVA (4)

http://www.spoj.com/problems/KOPC12A/ (4) //TS (sadly brute-force works too N^2)

</spoiler>

<spoiler summary="topo">

https://codeforces.com/gym/102058/problem/A (5) //[NICE][2TIMES][PRIORITY]

UVA	11686

LightOJ	1034

UVA	10305

124 &mdash; Following Orders [UVA]

200 &mdash; Rare Order [UVA]

872 &mdash; Ordering [UVA]

11060 &mdash; Beverages [UVA]

http://codeforces.com/contest/765/problem/E 5

http://codeforces.com/contest/770/problem/C 4 //reduce + toposort

http://codeforces.com/contest/825/problem/E 4 //Toposort from biggest/backward

http://www.spoj.com/problems/CODESPTI/ (6) //VERY NICE &mdash; Hard/Weak children

http://codeforces.com/contest/47/problem/B (2) //[EASY][Toposort on 3 elements]

http://codeforces.com/contest/909/problem/E (4) //[NICE][BFS][RECURSION]

</spoiler>

<spoiler summary="treap">

https://codeforces.com/contest/1181/problem/D (5) //[VERY NICE][SORTING][OFFLINE]

https://www.hackerrank.com/challenges/find-the-running-median/problem (4) //[NICE][HEAPS]

http://codeforces.com/gym/101992/problem/M (4) //[NICE][OFFLINE][SORTING]

http://codeforces.com/gym/100112 [C] (5) //[VERY NICE]

http://codeforces.com/gym/101864 [B] (5) //[NICE] Lesser than

http://codeforces.com/contest/899/problem/F (5) //[VERY NICE][DATA STRUCTURE] (FW or Treap)

http://codeforces.com/contest/879/problem/E (6) //[VERY NICE][Making somponents]

http://www.spoj.com/problems/ADAAPHID/ [or clever fenwick][or SQRT-tree]

http://www.spoj.com/problems/ADACROP/

http://codeforces.com/contest/762/problem/E 6

http://www.spoj.com/problems/COUNT1IT/ 5

http://www.spoj.com/problems/IITWPC4D/ 4 //From end &mdash; pick i-th + del i-th

http://www.spoj.com/problems/ALLIN1/ 4 //Typical treap operations

http://codeforces.com/contest/847/problem/D 5 //Prolly overkill &mdash; VERY NICE

http://codeforces.com/contest/863/problem/D 4 //Not desired solution

http://www.spoj.com/problems/KOILINE/ (4) //VERY NICE &mdash; Iterate from back &mdash; get+remove

http://www.spoj.com/problems/TWIST/ (5) //NICE: Reverse

http://www.spoj.com/problems/MEANARR/ (5) //VERY NICE! [POLICY][SHORT]

</spoiler>

<spoiler summary="tree">

http://www.spoj.com/problems/ADATOMEL/

https://codeforces.com/contest/1189/problem/D1 (4) //[OBSERVATION]

http://codeforces.com/contest/913/problem/B (2) //Simple check

http://codeforces.com/contest/894/problem/D (5) //[NICE][MERGING][BINARY]

http://codeforces.com/contest/746/problem/G 5

http://codeforces.com/contest/750/problem/F 9

http://www.spoj.com/problems/RTREE/ 3 //longest path tree &mdash; query

13175 UVA (2) //something like preorder build

http://codeforces.com/contest/796/problem/C (3) //Just counting &mdash; inc by at most 2

http://codeforces.com/contest/797/problem/D (4) //VERY NICE &mdash; sort + D&C all

http://codeforces.com/contest/805/problem/E (4) //NICE &mdash; Treewidth coloring (greedy)

http://codeforces.com/contest/828/problem/D (3) //Star construction

http://www.spoj.com/problems/TREEDEGREE/ (3) //Degree from euler tree

http://www.spoj.com/problems/UCV2013J/ (3) //Find what is leaf in Binary Tree

http://www.spoj.com/problems/GCPC11J/ (3) //Finding ceter

http://codeforces.com/contest/34/problem/D (3) //Simple reconstruction + DFS

</spoiler>

<spoiler summary="tree-dp">

http://www.spoj.com/problems/ADASALES/

https://codeforces.com/contest/1187/problem/E (5) //[VERY NICE][DFS]

http://www.spoj.com/problems/PT07X/ (4) //Classical- VC on tree [NICE]

http://codeforces.com/contest/81/problem/E (6) //[NICE][PSEUDOFOREST REDUCTION]

http://codeforces.com/contest/61/problem/D (4) //dfs-only might works too

LA 6631 - Jingle Balls (4) //[NICE][SIMPLE]

https://www.codechef.com/problems/TRANDED //By [user:sahil070197]

13089 &mdash; Golden Coins (UVA)

http://codeforces.com/problemset/problem/855/C

http://codeforces.com/problemset/problem/718/D

https://www.codechef.com/problems/TWOCOINS

https://www.hackerrank.com/contests/101hack35/challenges/road-maintenance/problem

7649 &mdash; Performance Review (LA)

http://codeforces.com/problemset/problem/741/D

http://codeforces.com/problemset/problem/592/D

https://www.codechef.com/problems/TOMJERGA

http://codeforces.com/problemset/problem/814/D

1220 &mdash; Party at Hali-Bula (UVA)

https://www.hackerrank.com/contests/june-world-codesprint/challenges/r-tree-decoration/problem

12452 &mdash; Plants vs. Zombies HD SP (UVA)

http://codeforces.com/problemset/problem/735/E

https://www.codechef.com/problems/COLTREE

12466 &mdash; Ancestors (UVA)

6829 &mdash; Intrepid climber (LA)

https://www.hackerrank.com/contests/101hack35/challenges/jeanies-route

12257 &mdash; The Queue (UVA)

http://codeforces.com/problemset/problem/805/F

http://codeforces.com/problemset/problem/763/D

1218 &mdash; Perfect Service

3346 &mdash; Perfect Domination on Trees (same as above -_-)

12093 &mdash; Protecting Zonk

10859 &mdash; Placing Lampposts

http://codeforces.com/problemset/problem/23/E //NICE [but requires big int]

http://codeforces.com/problemset/problem/14/D (5) //NICE [sorting-one][2DFS]

http://www.spoj.com/problems/TWOPATHS/ (6) //VERY NICE Same as above ~ bigger constraints

http://codeforces.com/contest/868/problem/E (8) //VERY NICE &mdash; HARD &mdash; on tree

</spoiler>

<spoiler summary="trie_bit">

https://www.spoj.com/problems/XORX/ (4) //[NICE][BASIC][PREFIXXOR]

http://codeforces.com/contest/888/problem/G (5) //NICE[BIT-BY-BIT D&C]

http://codeforces.com/contest/842/problem/D //Proposed by [user:usernameson]

http://codeforces.com/problemset/problem/706/D

https://www.hackerrank.com/contests/w8/challenges/black-box-1

https://csacademy.com/contest/round-42/task/xor-submatrix/

http://codeforces.com/contest/714/problem/C 5

http://www.spoj.com/problems/SUBXOR/ (4)

http://codeforces.com/contest/817/problem/E (5) //Classical &mdash; remember sum! NICE!

http://codeforces.com/contest/37/problem/C (4) //NICE &mdash; Prefix dictionary [or math]

</spoiler>

<spoiler summary="trie_string">

http://www.spoj.com/problems/ADAINDEX/

http://codeforces.com/gym/101628/problem/K (5) //[NICE][IMPLEMENTATION]

8015 - Alice and Bob play Contact (5) //[VERY NICE] 1stBob

2642 [LA]

UVA	10860

UVA	10295

UVA	13186 //+Bitset

UVA	1123

UVA	12506

UVA	11539

UVA	1142

UVA	12359

UVA	10282

11732 UVA (5)

11539 UVA (5)

11488 UVA (4)

http://www.spoj.com/problems/TRYCOMP/ (4)

10860 UVA (4) //DP + Trie [nice &mdash; slightly generic]

http://www.spoj.com/problems/DICT/ (4) //Sample trie &mdash; but slightly weak/wrong data-set

</spoiler>

<spoiler summary="TSP">

https://www.urionlinejudge.com.br/judge/en/problems/view/2810 (5) //[NICE][DOUBLE]

Gym	100818E [2015-2016 ACM-ICPC Southeastern European Regional Programming Contest (SEERC 2015)]

3725 [LA]

UVA	10496

Gym	101020H [2015 Syrian Private Universities Collegiate Programming Contest] N!

LightOJ	1057

UVA	11643 //[NICE][BFS]

3305 [LA] //On plane

10937 UVA (4) //find '!' / BFS / TSP &mdash; NICE!

10944 UVA (4)

10818 UVA (5) //Easy &mdash; but not-easy implementation: ++Dijkstra [LEX!]

http://www.spoj.com/problems/A_W_S_N/ (4) //BFS + TSP (path) &mdash; NICE

</spoiler>

<spoiler summary="two-pointers">

http://www.spoj.com/problems/ADAFENCE/ [Multiple Pointers]

http://www.spoj.com/problems/ADAPLANT/

https://codeforces.com/contest/1166/problem/C (4) //[CONDITION][OBSERVATION]

https://codeforces.com/contest/1148/problem/B (4) //[NICE][BS]

https://codeforces.com/contest/1175/problem/C (4) //[NICE][GREEDY]

https://codeforces.com/contest/1203/problem/D1 (4) //[VERY NICE][STRINGS][PREPROCESS]

https://codeforces.com/contest/1203/problem/D2 (5) //[VERY NICE][STRINGS][PREPROCESS]

https://codeforces.com/contest/1186/problem/C (4) //[VERY NICE][BITS][OBSERVATION]

https://www.spoj.com/problems/MOZHCAN/ (5) //[VERY NICE]

http://codeforces.com/gym/101864 [L] (4) //Static Size [SORTING]

Dev Skills-499: Closest Pair Point (4) //[NICE][GEOMETRY][STRUCTURES]

http://codeforces.com/contest/919/problem/C (3) //Similar - simple sweep [EASY]

http://codeforces.com/contest/144/problem/C (3) //[NICE][FREQUENCY][STRINGS]

http://codeforces.com/contest/895/problem/B (3) //[OR BS]

http://codeforces.com/contest/84/problem/B (2) //EASY //ll

http://codeforces.com/contest/79/problem/C (4) //NICE - [STRINGS][SET][COMPARE]

http://codeforces.com/contest/746/problem/F 6

11436 UVA (5)

http://codeforces.com/contest/760/problem/D 4

11386 UVA (4)

http://www.spoj.com/problems/WOWSUBSTR2/ 3

http://www.spoj.com/problems/ARRAYSUB/ 4

http://www.spoj.com/problems/CODFURY/ 3 //easy &mdash; ukazkove

http://codeforces.com/contest/769/problem/B 3 //sort + TP

http://codeforces.com/contest/814/problem/C 4 //NICE &mdash; maybe some DP +/-

http://www.spoj.com/problems/CRAN04/ 4 //NICE &mdash; (more or less) 3 pointers

http://www.spoj.com/problems/OPCPIZZA/ 3 //NICE [EASY] [AGAINS EACH OTHER]

http://www.spoj.com/problems/ALIEN/ (3) //Classical

http://www.spoj.com/problems/HOTELS/ (3) //Classical & Easy

http://www.spoj.com/problems/KOIREP/ (4) //VERY NICE &mdash; N buckedt find mid diff

http://codeforces.com/contest/6/problem/E (4) //NICE &mdash; Multiset

http://codeforces.com/contest/873/problem/C (3) //NICE &mdash; M times 2P tenchique

</spoiler>

<spoiler summary="wavelet_tree">

UVA	1480

http://www.spoj.com/problems/ILKQUERY/

http://codeforces.com/contest/840/problem/D //Proposed by [user:GreenGrape]

</spoiler>

<spoiler summary="Zfunction">

https://www.codechef.com/problems/CHSTR //Proposed by [user:Apptica]

http://www.spoj.com/problems/SUFEQPRE/

http://codeforces.com/problemset/problem/126/B

http://codeforces.com/contest/119/problem/D (7) //[VERY NICE]

</spoiler>

<spoiler summary="2SAT">

https://www.urionlinejudge.com.br/judge/en/problems/view/1348 (4) //[CLASSICAL][NICE][SCC]

11930 UVA (4)

http://codeforces.com/contest/776/problem/D (5)

</spoiler>

Finally if you would like to add some problem to the list &mdash; even though I would be glad, please do so only in case of:

1. It is very interesting

2. There is nothing, or low number of problems in the topic

3. You add it in "bigger amount" at once

Thank you.

Offcourse if you have any remarks, questionns or requests, don't hesitate to ask.

PS: I'm sorry but there might be some duplicities. In that case, either report it or ignore it (unless they are in different topics, then it have reason :) )

Good Luck & Have Nice Day