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| @@ -0,0 +1,69 @@ | ||
| package me.gergo | ||
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| import java.io.File | ||
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| fun main() { | ||
| val blizzardLines = File("src/main/resources/input24.txt").readLines() | ||
| val width = blizzardLines[0].length - 2 | ||
| val height = blizzardLines.size - 2 | ||
| val blizzards = blizzardLines.mapIndexed(::parseBlizzards).flatten() | ||
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| // Pre-calculating all possible blizzard states, exploiting the fact that the move in modulo, so their lowest common multiple of the rows/cols | ||
| // will generate all the possible states | ||
| val blizzardStateCount = lcm(width, height) | ||
| val blizzardStates = Array(blizzardStateCount) { t -> | ||
| val map = Array(height) { BooleanArray(width) { false } } | ||
| for (b in blizzards) { | ||
| var x = b.x | ||
| var y = b.y | ||
| when (b.direction) { | ||
| Direction.L -> x -= t | ||
| Direction.U -> y -= t | ||
| Direction.R -> x += t | ||
| Direction.D -> y += t | ||
| } | ||
| map[Math.floorMod(y, height)][Math.floorMod(x, width)] = true | ||
| } | ||
| map | ||
| } | ||
| println("Pre-generated ${blizzardStates.size} states") | ||
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| var states = setOf(State24(0, 0, 1)) | ||
| for (t in 1..Int.MAX_VALUE) { | ||
| println("Minute $t, number of states: ${states.size}") | ||
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| val newStates = HashSet<State24>(states.size) | ||
| val bsNext = blizzardStates[(t + 1) % blizzardStateCount] | ||
| for (s in states) { | ||
| // Moving in any direction is an option if there will be no blizzard there in the next round | ||
| if (s.x > 0 && bsNext.free(s.x - 1, s.y)) newStates.add(State24(s.x - 1, s.y, t + 1)) | ||
| if (s.y > 0 && bsNext.free(s.x, s.y - 1)) newStates.add(State24(s.x, s.y - 1, t + 1)) | ||
| if (s.x < width - 1 && bsNext.free(s.x + 1, s.y)) newStates.add(State24(s.x + 1, s.y, t + 1)) | ||
| if (s.y < height - 1 && bsNext.free(s.x, s.y + 1)) newStates.add(State24(s.x, s.y + 1, t + 1)) | ||
| // Staying in place is only an option if there will be no blizzard in the next round | ||
| if (bsNext.free(s.x, s.y)) newStates.add(State24(s.x, s.y, t + 1)) | ||
| } | ||
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| if (newStates.any { s -> s.x == width - 1 && s.y == height - 1 }) { | ||
| println("Goal reached at: ${t + 2}") // We've started from (0,0) and ended up in (width-1,height-1) | ||
| break | ||
| } | ||
| states = newStates | ||
| } | ||
| } | ||
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| private fun Array<BooleanArray>.free(x: Int, y: Int) = !this[y][x] | ||
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| private data class State24(val x: Int, val y: Int, val time: Int) | ||
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| private data class Blizzard(val x: Int, val y: Int, val direction: Direction) | ||
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| private fun parseBlizzards(y: Int, line: String) = line.mapIndexedNotNull { x, c -> | ||
| when (c) { | ||
| '^' -> Blizzard(x - 1, y - 1, Direction.U) | ||
| 'v' -> Blizzard(x - 1, y - 1, Direction.D) | ||
| '<' -> Blizzard(x - 1, y - 1, Direction.L) | ||
| '>' -> Blizzard(x - 1, y - 1, Direction.R) | ||
| else -> null | ||
| } | ||
| } |
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| #.###################################################################################################################################################### | ||
| #.v><><<>^^^<><<>.^v<>v^>v^v^^<..^v>^>^vv.>v^<<>^.v<vvv<.>><v>><^>><>^<><v<>>>><v>v<^<>^.v..v^vv<v<<vv.v>>v<>v.<..^<vv<^v^v.v>>v>><^v>^<.vv^^<<><<>v>><# | ||
| #.vv<vv<>.v<<<<<>>vv<>^v^^<^<>><.<^>^<^>^<v<<<<v>v>><.><.^><>vv<^^><<<<>^<.<v^.vv^vv>v>^.<<<><v<.v.<><<v^^v>^^<^>>^.<v^v.v><<v^vv<<v>^v>><^^<^<v>^>><v<# | ||
| #<v^>v^vv<><v><<^<>^<^vv>v>>^^><<<vv><v.v.^><<^><>v>^<^v<<^>v<vv><v<<^.vv^>>>.^v>v.><v>v<^<^^<><<>><<^^^>v<^>>^v>>vv.<>^<><<^v>><^.>v^v><<^^^^<v<>^v<v.# | ||
| #<<^<vv^<^><>^><>^vv.v^v>><^^<>^<>>^><^.^^<.v...>^^.^<<v<vvv>>>v^..^v.v<^><>.>v^.vv<^^vv>vv^.^.vv<v>>^>v.^^^<v<>><vv^>>^^.v>.v^^<^>vvv^<<v^<v<^><^>v<>># | ||
| #<.<^>>^<v><^>^^.>>v^<v^vvv>>vv.v^<>^^>v<<vv^<>^v.<<<^>>>.^>vvv.^^^<^><<^><v>><^.^>vv^^vv.><<v<^<v^^^.>v>^>v.^^<<^^^>^><><<vv<.<>v>vv>><^^v>>vvv^<...<<# | ||
| #><v.v>vv>^^^>>><v>^^v>^>>><vv^<^<^<<<>.<<.<.<..><><v.v^^.v..v^>>>^v><.^^><<>v^<^<>^>>.v^v.v.>v>^>>>v>>^>><^<.v.v<^<<<<<^^>^^^^>^^<v^>>v><>.<>v><>.>><># | ||
| #<><<.>^<>^^v<v>^><^>v^.>><vv^vv^<v<<>.>.>>.vv.v<.^<^<>>^><><^.v>>v^^v><>><<<vv<<>v><>^.>>^>v^^><^<v<<><vv^>>.<^<.^<^>vvv>^<.v<^<>.><.>>v<^>^v<<.^<v>^<# | ||
| #<>.<v^>.^<<^v^.<<^>v^^vv<^><^<^>><v^^vvv<<vvvv>>^v><<>^>vvvvv^<<v^.>^<.<^>.^>^><v^<>>.<<^^vv>>>^>vv><vvv^v.>^vv><<<<>^v^^^.>.^>>^^v^v>v>vv^<<^vv^<>v<># | ||
| #<<>v>v>>v^^v><^<.vv<^>^^>.v^<.^^vv>.<>^<>v>^>vvv<vv^>v^><<<v>vv<..^v^v>v.v><^.<^>.v<v><v>v^>^<<<<<>^.v<^.<v.<<^>v^^^<^<<>v.<<^<<<<.<^><<<^<v<v>>v>.><># | ||
| #>>.>vvv<<..>^^vv^>.<.v..v^^>^v<<>>>vv.<v>vv^<vv^v><v^^.<<.><..><^><<>^<<><v<.<v.<^<^.^<^<<><><<^v^>.<<v^^>.^<...v.^<^^<><><>v^<><^>^>^v^.>^^>^.vv.<v^># | ||
| #>.<><v>v<v>v>^v^^v>.v^.v>v>.<>>>^vv<<v>>^>^.^<^vv.vvvv<<>v<^^.>v<^v<<^><^.^^v<>.v<vv><v<v>vvv>^^>v>..<<<v..>v..<^^^<v>^^<<vv<>>^^v^.vv<><^>>.^<<^>>v.># | ||
| #><v..vv^<v^<>>v<>..<^>v^^><.>vv^vv^<^^v<>vv<.vv^^<>^>>^v<^^<<>^vv>v><>v<^vvv^<>><>^^^v^<v.v^<<^^>>>>><^^>><^v>>vv^v><^>^<<^.v>vv>^.v^<vv^v>>>vv>v^v<^># | ||
| #...>><v.<v<>^.v.v..^>^<><vv^><<<vv^<vv.><^.vv>>><v^v^>^v>>v<.^<^^<v^<>v<^<><<<.^<<vv.<>>^v^^.v>.<v>^.^>v^.v><^<<>>>^.<<<^v<<<><^>.^.^v><>^>><vv<v.<.^># | ||
| #<^vv>>v>v<^><^^^<^>vv<>vv>^^^.><><^>v>><v.<>vv^^<^<<<v^<><v>v^v>^<><><><><>^^>><>..^^>v<...vv<^>><.vv<^<v><v<vv^.><>v^<>v.^>>>v<<^<<^vv.>^<.^<>^<v^^^># | ||
| #>>^vv^.<<.<.<>>vvv<<<..<v><^<>^><<>^.<<^^^<v^<<v.<vv<^<>>vv^>.v^v<^<>>vv<<^>>.v>.v>^^^vvv^v<^><v^><>><^<.>v^^^<vv^>^v<v^<vv><>..^><.>^^<^>>..^.v^<^<v># | ||
| #<<><^^><v^v<^^<vv>><v..>>>^><>>>v>v>v>v><>>^vv><>>v>>vvvv<<^><>v^>vv>^.>>v.^<v<^.>>>^^v>>><vvv>><.<v<^<v<^v<v<<vvv..^^<<^<.<><<<<^<>v<<<^^>.^v>^^v<^^<# | ||
| #>v^^^<v>^^<v<<<vv><^v.v<v^^^vvv<<><><^^><^^>>>>>><^>^^.>vv>^><<<v<<<^vv.^^^<v>v<^^^^>.^^vv<^<.<v^<vv^^^>><..><^>v><<v>v>^v^>>^^>vv.v^^^>^^vv.<<v.^><<.# | ||
| #<^v<<^^vvv.>v>v>.v><v<^^>^>^>^^v>v^vv^<.^.>>>>>v<>.<<.<^<<vvv..<^>^><^>^<^<<>><^>v<v^v>^v^^^>>>>v>^>>^<v..><.>>^^><^<^.<v^>^.v>^^vv^v.<>>>>.v.<<>^^vv># | ||
| #<v^v.>.>^v>^<v.<^<^>v^>^^.>.>v<>>>^>vv<>v<>^>v^<<^<.<<^>v^<><>><^^<^^v<>>vv<<.<>v>.>^^^>><^^<^vv.><v<.<<^^>^>><>v><^vv.>v^v^v..<vvv..<<v<v^<<v>^<^>><<# | ||
| #<^v<v^^v^>^<>v^<^<>>..>><>v<.^<.>v.>^v.>>^^<^v>>v^.v>^><>>vv.<<<>v>^.>v>..<<<v.<v^<>^>^<>v<^<v<><^>^v><.<<^^^<^.<<<^.^v^^.>^.<<vv>^v><<>^<^v^^>^v><<^># | ||
| ######################################################################################################################################################.# |