1. // Wrap in object, otherwise ammonite .par or Future would not work
  2. object Solution {
  4. val O = scala.io.Source.fromFile("input").getLines.map(_.toCharArray).toArray
  6. //FIXME: This M is global variable entangled in case class S for defining empty etc.
  7. // Also this is used in findStable which is sad.
  8. var M = O
  9. val R = M.length
  10. val C = M.head.length
  12. case class S(r: Int, c: Int) {
  14. def +(o: S) = S(r + o.r, c + o.c)
  16. def ok = r >= 0 && r < R && c >= 0 && c < C
  18. def empty = M(r)(c) == 'L'
  19. def occupied = M(r)(c) == '#'
  20. def floor = M(r)(c) == '.'
  22. def dbg = s"$r $c ${M(r)(c)}"
  24. def update(v: Char, n: Array[Array[Char]]) = n(r)(c) = v
  25. }
  27. val NB = List(
  28. S(-1, -1), S(-1, 0), S(-1, 1),
  29. S( 0, -1), S( 0, 1),
  30. S( 1, -1), S( 1, 0), S( 1, 1)
  31. )
  33. val coords = for (r <- 0 to R - 1; c <- 0 to C - 1) yield (r, c)
  35. // direct 8 neighbours
  36. def seen1(cur: S) = NB.map(_ + cur).filter(_.ok).filter(_.occupied).size
  37. // closest 8 direction neighbours
  38. def seen2(cur : S) = {
  39. var seen : List[S] = Nil
  41. NB.foreach{ dir =>
  42. var c = cur + dir
  43. while(c.ok && c.floor){
  44. c += dir
  45. }
  46. if(c.ok) seen = c :: seen
  47. }
  49. seen.filter(_.occupied).size
  50. }
  51. def evolve(fSeen : S => Int, minSeen : Int) = {
  52. var stable = true
  53. val N = M.map(_.clone)
  54. val updates = coords.par.map { case (r,c) =>
  55. val cur = S(r,c)
  56. val nSeen = fSeen(cur)
  57. if(cur.empty && nSeen == 0) {
  58. cur.update('#', N)
  59. stable = false
  60. }
  61. if(cur.occupied && nSeen >= minSeen) {
  62. cur.update('L', N)
  63. stable = false
  64. }
  65. }
  66. M = N
  67. stable
  68. }
  69. def findStable(fSeen : S => Int, minSeen : Int): Int = {
  70. M = O
  71. var stable = evolve(fSeen, minSeen)
  72. while(!stable){ stable = evolve(fSeen, minSeen) }
  73. M.flatten.filter(_ == '#').size
  74. }
  75. def solveAll() = {
  76. println(findStable(seen1, 4))
  77. println(findStable(seen2, 5))
  78. }
  79. }
  81. Solution.solveAll()