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  1. NB. Solutions to Advent of Code 2017 puzzles
  2.  
  3. NB. Most of the input can be formatted using ". if an array or number is required.
  4.  
  5. NB. Day One, parts one and two. Apply to a 1D array.
  6.  
  7. day1p1 =: 3 : '-:+/(+/*=/)"1(y{~(,((#y)&|)@>:))"0 i.#y'
  8.  
  9. day1p2 =: 3 : '-:+/(+/*=/)"1(y{~(,((#y)&|)@(+&(-:#y))))"0 i.#y'
  10.  
  11. NB. Day Two, parts one and two. Apply to a matrix.
  12.  
  13. day2p1 =: +/@:((>./ - <./)"1)
  14.  
  15. day2elf =: 3 : '%/({~(|:@:((<.@(%&(#y))),((#y)&|))@:((i.&0)@:,@:((=/~@:i.@#)+(||:)@:($~,~@#))"1)))y'
  16. day2p2 =: +/@:(day2elf"1)
  17.  
  18. NB. Day Three. Apply directly to a number.
  19.  
  20. day3p1 =: >.@-:@<:@%:+<./@:|@(-(*:@<:@+:+*&(>:+:i.4))@>.@-:@<:@%:)
  21.  
  22. day3p2 =: 3 : '({~ (i.&0)@:(y&>))/:~,(,+/\@:(3+/\(0&,)@:(,&0)@:{:))@:(|:@:|.)^:((2&+)>.^.y)(1 1$1)'
  23. NB. Day Four. Apply to a multi-line string
  24.  
  25. day4p1 =: +/@:((#=#@~.)@(>@;:@>)"0)@cutopen
  26.  
  27. day4p2 =: +/@:((#=#@~.)@:(/:~"1)@(>@;:@>)"0)@cutopen
  28.  
  29. NB. Day Five. Apply to a list
  30.  
  31. day5p1 =: 3 : 0
  32. a =. y
  33. pos =. 0
  34. c =. 0
  35. while. pos e. i.#a do.
  36.         a =. (>: pos{a) pos} a
  37.         pos =. pos + <: pos{a
  38.         c =. >:c
  39. end.
  40. c
  41. )
  42.  
  43. day5p2 =: 3 : 0
  44. a =. y
  45. pos =. 0
  46. c =. 0
  47. while. pos e. i.#a do.
  48.         g =. (>&2) pos{a
  49.         a =. (>:(<:@<:^:g) pos{a) pos} a
  50.         pos =. <:(>:@>:^:g) pos + pos{a
  51.         c =. >:c
  52. end.
  53. c
  54. )
  55.  
  56. NB. Day 6. Takes part (1 or 2) as left argument, list as right (warning: slow)
  57. NB. Formatting the input was a bit odd, I used the following:
  58. NB. , ". > cutopen 1!:1 < '/path/to/input/text'
  59.  
  60. day6 =: 4 : 0
  61. s =. |: ,. y
  62. while. -. ({:s) e. }:s do.
  63.         s =. (, (0&(((i. >./){:s)})+(<:@-@(i.~&({:s)) |. +/@((,&(#{:s)) $!.0 (%~@:>:@i.)))@(>./))@:{:) s
  64. end.
  65. 1-~(#s)-(x-1)*(s i. {:s)
  66. )
  67.  
  68. NB. Day 8.
  69.  
  70.  
  71. NB. Day 10.
  72. NB. Helper functions: convert to hex string, and bitwise xor
  73.  
  74. hex =: ,@:(":@({&a.@:(87&+)^:(> 9:))"0)@:(16 16&(#.^:_1))
  75.  
  76. xor =: #.@((8$2)&#:@[ (+. *. -.@*.) (8$2)&#:@])
  77.  
  78. NB. The main function. Takes part number as left argument.
  79.  
  80. day10 =: 4 : 0
  81. l =. (,&(17 31 73 47 23)@:(a.&i.))^:(<:x) y
  82. vals =. i.256
  83. pos =. 0
  84. skp =. 0
  85. rnd =. 0
  86. whilst. (<:x) *. rnd < 64 do.
  87.         len =. 0
  88.         while. len < #l do.
  89.                 vals =. (pos, len{l) (-@{.@[ |. {:@[ (|.@{. , }.) {.@[ |. ]) vals
  90.                 pos =. pos + skp + len{l
  91.                 skp =. >:skp
  92.                 len =. >:len
  93.         end.
  94.         rnd =. >:rnd
  95. end.
  96. (*/@:(2&{.))`(,@:(hex"0)@:(xor/"1)@:((16 16)&$)) @. (<:x) vals
  97. )
  98.  
  99. NB. Day 13.
  100.  
  101. day13p1 =: +/@:((*/ * 0: = 2&*@<:@{: | {.)"1@:((".@}:@>@{. , ".@>@{:)"1)@;:@>@cutopen)
  102.  
  103. day13p2 =: (<0 0)&{@:((>:@{. , {:)"1^:(+./@:((0: = 2&*@<:@{: | {.)"1)@:])^:_)@:((".@}:@>@{. , ".@>@{:)"1@;:@>@cutopen)
  104.  
  105. NB. Day 14.
  106.  
  107. NB. Builds disk of 1s and 0s
  108.  
  109. disk =: 3 : 0
  110. in =. y , '-'
  111. row =. 0
  112. dsk =. ,.i.0
  113. while. row < 128 do.
  114.         dsk =. dsk, (,@:((4#2)&#:"0)@:((".`((-&87)@:(a.&i.))@.(e.&'abcdef'))"0)@:(2&day10)) (in,":row)
  115.         row =. >:row
  116. end.
  117. dsk
  118. )
  119. NB. Part 1.
  120.  
  121. day14p1 =: +/@:(+/@:disk)
  122.  
  123. NB. Flood fill algorithm, for part 2.
  124.  
  125. flood =: 4 : 0
  126. node =. 2{.y
  127. if. (*./ node < $x) *. (*./ node >: 0 0) do.
  128.         color =. (<node) { x
  129. else.
  130.         color =. {:y
  131. end.
  132. if. color = 2{y do.
  133.         x =. ({:y) (<node)} x
  134.         x =. (flood&((node - 0 1),(_2{.y)))@:(flood&((node - 1 0),(_2{.y)))
  135.         x =. (flood&((node + 0 1),(_2{.y)))@:(flood&((node + 1 0),(_2{.y)))
  136.         x
  137. else.
  138.         x
  139. end.
  140. )
  141. NB. Part 2. Left argument of 1 makes the disk be output, good with viewmat. Otherwise put 0.
  142.  
  143. day14p2 =: 3 : 0
  144. dsk =. -. disk y
  145. reg =. 0
  146. while. 0 e. , dsk do.
  147.         reg =. <:reg
  148.         ind =. (#@[ ((<.@%~) , |) (i.&0)@,@])~ dsk
  149.         dsk =. dsk flood ind,0,reg
  150. end.
  151. if. x = 1 do.
  152.         dsk
  153. else.
  154.         -reg
  155. end.
  156. )
  157.  
  158.  
  159. NB. Day 15. Slow. Apply to a list of (starting A value , starting B value)
  160.  
  161. day15p2 =: 3 : 0
  162. valA =. {.y
  163. valB =. {:y
  164. factA =. 16807x
  165. factB =. 48271x
  166. mod =. 2147483647x
  167. pair =. 0
  168. count =. 0
  169. valsA =. i.0
  170. valsB =. i.0
  171. while. pair < 5e6 do.
  172.         valA =. mod | factA * valA
  173.         valB =. mod | factB * valB
  174.         if. 0 = 4 | valA do.
  175.                 valsA =. valsA , valA
  176.         end.
  177.         if. 0 = 8 | valB do.
  178.                 valsB =. valsB , valB
  179.         end.
  180.         if. ((#valsA) > 0) *. ((#valsB) > 0) do.
  181.                 pair =. >:pair
  182.                 count =. count + ((2^16) | {.valsA) = ((2^16) | {.valsB)
  183.                 valsA =. }.valsA
  184.                 valsB =. }:valsB
  185.         end.
  186. end.
  187. count
  188. )
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