### 341 Flatten Nested List
377 Combination Sum IV
398 Random Pick Index
404 Sum of Left Leaves
1 Two Sum 23.0% Easy
### 10 Regular Expression Matching 22.0% Hard
13 Roman to Integer 39.2% Easy
15 3Sum 18.8% Medium
17 Letter Combinations of a Phone Number 28.6% Medium
20 Valid Parentheses 29.3% Easy
### 23 Merge k Sorted Lists 23.3% Hard
25 Reverse Nodes in k-Group 27.5% Hard
26 Remove Duplicates from Sorted Array 33.4% Easy
28 Implement strStr() 24.8% Easy  pi(n,0)
### 33 Search in Rotated Sorted Array 30.2% Hard f(a[0] - a[i] < 0)
38 Count and Say 28.9% Easy
43 Multiply Strings 23.4% Medium
44 Wildcard Matching 17.4% Hard leetcode for #10
49 Group Anagrams 27.4% Medium count sort
50 Pow(x, n) 27.9% Medium
### 56 Merge Intervals 25.3% Hard
57 Insert Interval 23.8% Hard
67 Add Binary 27.4% Easy
69 Sqrt(x) 25.2% Medium
71 Simplify Path 21.9% Medium
75 Sort Colors 34.7% Medium   part qsort
76 Minimum Window Substring 21.2% Hard
78 Subsets 31.3% Medium
79 Word Search 22.9% Medium = #, rec, = temp
80 Remove Duplicates from Sorted Array II 32.7% Medium
85 Maximal Rectangle 23.4% Hard
88 Merge Sorted Array 30.0% Easy
90 Subsets II 30.5% Medium
91 Decode Ways 17.5% Medium
98 Validate Binary Search Tree 20.9% Medium
102 Binary Tree Level Order Traversal 32.7% Easy
117 Populating Next Right Pointers in Each Node II 32.8% Hard
121 Best Time to Buy and Sell Stock 36.0% Easy
125 Valid Palindrome 23.8% Easy
127 Word Ladder 19.6% Medium
128 Longest Consecutive Sequence 32.1% Hard
133 Clone Graph 24.9% Medium
139 Word Break 25.2% Medium
146 LRU Cache 15.8% Hard
157 Read N Characters Given Read4 29.5% Easy
158 Read N Characters Given Read4 II – Call multiple times 23.4% Hard
161 One Edit Distance 28.4% Medium
168 Excel Sheet Column Title 21.6% Easy --n;
173 Binary Search Tree Iterator 34.5% Medium
200 Number of Islands 27.6% Medium
206 Reverse Linked List 39.4% Easy
208 Implement Trie (Prefix Tree) 25.3% Medium
209 Minimum Size Subarray Sum 26.8% Medium
210 Course Schedule II 21.0% Medium
211 Add and Search Word – Data structure design 20.2% Medium
215 Kth Largest Element in an Array 33.1% Medium
218 The Skyline Problem 22.0% Hard
221 Maximal Square 23.5% Medium
234 Palindrome Linked List 28.0% Easy
235 Lowest Common Ancestor of a Binary Search Tree 37.7% Easy
236 Lowest Common Ancestor of a Binary Tree 28.8% Medium
238 Product of Array Except Self 42.6% Medium
252 Meeting Rooms 41.6% Easy
253 Meeting Rooms II 34.6% Medium
257 Binary Tree Paths 28.4% Easy
261 Graph Valid Tree 32.5% Medium
265 Paint House II 35.6% Hard
269 Alien Dictionary 22.9% Hard
273 Integer to English Words 18.7% Hard
274 H-Index 29.3% Medium
275 H-Index II 32.5% Medium
277 Find the Celebrity 35.1% Medium
278 First Bad Version 22.4% Easy
282 Expression Add Operators 24.8% Hard
283 Move Zeroes 44.0% Easy
285 Inorder Successor in BST 35.6% Medium
286 Walls and Gates 37.2% Medium
297 Serialize and Deserialize Binary Tree 27.8% Hard
301 Remove Invalid Parentheses 31.9% Hard
311 Sparse Matrix Multiplication 47.2% Medium
314 Binary Tree Vertical Order Traversal 30.3% Medium
325 Maximum Size Subarray Sum Equals k 39.9% Easy
334 Increasing Triplet Subsequence 33.2% Medium