1. import scala.collection.mutable.{Map => MMap}
  2. import scala.collection.mutable.{Set => MSet}
  4. object Wrapper {
  5. // 0 1 2 3 4 5 6 7
  6. // 0 1 2 3 4 5 6 7
  7. // 0 1 2 3 4 5 6 7
  8. // 0 1 2 3 4 5 6 7
  9. val dy = Array( 0, 0, -1, -1, 1, 1)
  10. val dx = Array( 1, -1, 1, 0, 1, 0)
  12. // Took ages to realize that dx depends on the Y
  13. val dxx = Array( 1, -1, 0, -1, 0, -1)
  15. val mv = Array( "e", "w","ne","nw","se","sw")
  17. val lines = scala.io.Source.fromFile("input").getLines.toArray
  19. def part1(lines: Array[String]) = {
  21. val tiles = MMap[(Int, Int), Int]()
  23. lines.foreach { line =>
  24. var moves = line
  25. var x = 0
  26. var y = 0
  27. while(!moves.isEmpty){
  28. for(m <- 0 until 6){
  29. if(moves.startsWith(mv(m))){
  30. if(y%2 == 0)
  31. x += dx(m)
  32. else
  33. x += dxx(m)
  34. y += dy(m)
  35. moves = moves.substring(mv(m).length)
  36. }
  37. }
  38. }
  39. if(tiles.contains(x->y)){
  40. tiles(x->y) = 1 - tiles(x->y)
  41. } else {
  42. tiles(x->y) = 1
  43. }
  44. }
  45. println(tiles.values.sum)
  46. tiles
  47. }
  49. def neighbours(x: Int, y:Int) = {
  50. (0 until 6) map { m =>
  51. val xx = x + (if(y%2 == 0) dx(m) else dxx(m))
  52. val yy = y + dy(m)
  53. (xx, yy)
  54. }
  55. }
  57. def part2(tiles: MSet[(Int, Int)]){
  59. var cur = tiles.clone
  60. var next = MSet[(Int, Int)]()
  62. for(turn <- 1 to 100){
  63. val whites = MSet[(Int, Int)]()
  64. next = MSet[(Int, Int)]()
  65. cur.foreach { case (x, y) =>
  66. val nb = neighbours(x,y).toSet
  67. val blacks = nb.filter(cur)
  68. if(!(blacks.size == 0 || blacks.size > 2))
  69. next += x -> y
  70. whites ++= nb
  71. }
  72. whites --= cur
  73. whites.foreach { case (x, y) =>
  74. val nb = neighbours(x,y)
  75. val blacks = nb.filter(cur)
  76. if( blacks.size == 2)
  77. next += x -> y
  78. }
  79. cur = next.clone
  80. }
  81. println(cur.size)
  82. }
  83. def solve() = {
  84. val tiles = part1(lines).filter(_._2 == 1)
  85. val blacks = MSet[(Int, Int)]()
  86. blacks ++= tiles.keySet
  87. part2(blacks)
  88. }
  89. }
  90. Wrapper.solve()