Day 18

src/main/kotlin/com/basdado/adventofcode/Day18.kt

@@ -0,0 +1,184 @@
+package com.basdado.adventofcode
+
+import java.util.stream.Collectors
+import kotlin.system.measureTimeMillis
+
+const val DAY18_INPUT = "/day/18/input.txt"
+
+fun main() {
+
+    val day = Day18()
+    day.puzzle1()
+    println("Puzzle 2 took " + measureTimeMillis { day.puzzle2() } + " ms")
+}
+
+class Day18 {
+
+    fun puzzle1() {
+
+        val area = parseInput()
+
+        val afterTime = evaluateTime(area, 10)
+
+        val lumberCount = afterTime.area.count { it == AcreType.LUMBERYARD }
+        val treeCount = afterTime.area.count { it == AcreType.TREES }
+
+        println(lumberCount * treeCount)
+    }
+
+    fun puzzle2() {
+
+        val area = parseInput()
+
+        val afterTime = evaluateTime(area, 1000000000)
+
+        val lumberCount = afterTime.area.count { it == AcreType.LUMBERYARD }
+        val treeCount = afterTime.area.count { it == AcreType.TREES }
+
+        println(lumberCount * treeCount)
+    }
+
+    private fun evaluateTime(area: LumberArea, minutes: Int): LumberArea {
+
+        var oldArea = area.clone()
+
+        val seen = mutableMapOf(Pair(area, 0))
+
+        var minute = 1
+        while(minute <= minutes) {
+
+            val newArea = LumberArea(area.width, area.height)
+
+            for (y in 0 until oldArea.height) {
+                for (x in 0 until oldArea.width) {
+                    when (oldArea.get(x, y)) {
+                        AcreType.OPEN -> newArea.set(
+                            x, y,
+                            if (oldArea.countAdjacent(x, y, AcreType.TREES) >= 3)
+                                AcreType.TREES
+                            else
+                                AcreType.OPEN
+                        )
+                        AcreType.TREES -> newArea.set(
+                            x, y,
+                            if (oldArea.countAdjacent(x, y, AcreType.LUMBERYARD) >= 3)
+                                AcreType.LUMBERYARD
+                            else
+                                AcreType.TREES
+                        )
+                        AcreType.LUMBERYARD -> newArea.set(
+                            x, y,
+                            if (oldArea.countAdjacent(x, y, AcreType.LUMBERYARD) >= 1 && oldArea.countAdjacent(
+                                    x,
+                                    y,
+                                    AcreType.TREES
+                                ) >= 1
+                            ) {
+                                AcreType.LUMBERYARD
+                            } else {
+                                AcreType.OPEN
+                            }
+                        )
+                    }
+                }
+            }
+
+            val repeatingMinute = seen[newArea]
+            if (repeatingMinute != null) {
+                val repeatLength = minute - repeatingMinute
+                val cycleSkip = ((minutes - minute) / repeatLength) * repeatLength
+                println("Found cycle of $repeatLength minutes between $minute and $repeatingMinute, skipping $cycleSkip")
+                minute += cycleSkip
+                seen.clear()
+            }
+
+            seen[newArea] = minute
+
+            oldArea = newArea
+
+            minute++
+        }
+        return oldArea
+    }
+
+    fun parseInput(): LumberArea {
+
+        val input = lines(DAY18_INPUT).collect(Collectors.toList())
+
+        val res = LumberArea(input[0].length, input.size)
+        for (y in 0 until input.size) {
+            for(x in 0 until input[y].length) {
+                res.set(x, y, acreType(input[y][x]))
+            }
+        }
+        return res
+    }
+
+    fun acreType(c: Char): AcreType = AcreType.values().find { it.char == c }!!
+
+    enum class AcreType(val char: kotlin.Char) {
+        OPEN('.'), TREES('|'), LUMBERYARD('#')
+    }
+    class LumberArea(val width: Int, val height: Int, val area: Array<AcreType> = Array(width * height) { AcreType.OPEN }) {
+
+        private fun index(x: Int, y: Int): Int = y * width + x
+        fun get(x: Int, y: Int): AcreType {
+            return if (x !in 0 until width || y !in 0 until height)
+                AcreType.OPEN
+            else
+                area[index(x, y)]
+        }
+        fun set(x: Int, y: Int, acre: AcreType) {
+            area[index(x, y)] = acre
+        }
+
+        fun countAdjacent(x: Int, y: Int, type: AcreType): Int {
+            return (if (get(x + 1, y) == type) 1 else 0) +
+                    (if (get(x + 1, y + 1) == type) 1 else 0) +
+                    (if (get(x, y + 1) == type) 1 else 0) +
+                    (if (get(x - 1, y + 1) == type) 1 else 0) +
+                    (if (get(x - 1, y) == type) 1 else 0) +
+                    (if (get(x - 1, y - 1) == type) 1 else 0) +
+                    (if (get(x, y - 1) == type) 1 else 0) +
+                    (if (get(x + 1, y - 1) == type) 1 else 0)
+        }
+
+
+
+        override fun toString(): String {
+
+            val res = StringBuilder()
+            for(y in 0 until height) {
+                for(x in 0 until width) {
+                    res.append(get(x, y).char)
+                }
+                res.append("\r\n")
+            }
+            return res.toString()
+        }
+
+        override fun equals(other: Any?): Boolean {
+            if (this === other) return true
+            if (javaClass != other?.javaClass) return false
+
+            other as LumberArea
+
+            if (width != other.width) return false
+            if (height != other.height) return false
+            if (!area.contentEquals(other.area)) return false
+
+            return true
+        }
+
+        override fun hashCode(): Int {
+            var result = width
+            result = 31 * result + height
+            result = 31 * result + area.contentHashCode()
+            return result
+        }
+
+        fun clone(): LumberArea {
+            return LumberArea(width, height, area.clone())
+        }
+    }
+}

src/main/resources/day/18/example.txt

@@ -0,0 +1,10 @@
+.#.#...|#.
+.....#|##|
+.|..|...#.
+..|#.....#
+#.#|||#|#|
+...#.||...
+.|....|...
+||...#|.#|
+|.||||..|.
+...#.|..|.

src/main/resources/day/18/input.txt

@@ -0,0 +1,50 @@
+.|#.#|..#...|..##||...|#..##..#..|#|....#.#|.|....
+.||....#..#...|#....#.||....||...||...|..#|..||..|
+......|.|.#.#.#..|.....#.###.....#........|.||..#|
+..|.....||...#||#.#|#.....|##.|.|....|#....#|..#.#
+|...#.|..#|#.#....|.#.#.|.#...#..#|#.....##|#..#.|
+#....|#|......#.|||..#..#..||...#.#...|||##|..|#..
+.#||.|....|.......#|##...|.#.....#.##...|.|.#...#|
+....#|.|.|...##.......|#.....|..#......#...#|.#..#
+...#.|....#.|.#...|||......##..|#|||#..#...|.|#.#.
+.#..|...|..#.|##.#.#......#...||.||.#...|.#.#.#|..
+|...#.|||...#|.#||.......|.##.....|..||...####...|
+.##..|..##|...##.#...#...#.#|.|###...#............
+|.....||...#.......|.#..|#.....|.|#.|..||.##.|#|..
+.#..##|.#|.|..|.#..#.|.#..#|......##...#.#.......#
+...#.##.|..|.#.....#....#..#.............|.|##||..
+||.##.||.|.|..|..#.|.|.##|.|...|.#.|#.......#.|...
+..|#.##..#|.#|#.#...........|.|........#...#|...#|
+....|.#|..|.#|#|...|.|.#..#.....#|##|||##.#....#..
+...###.#.....#.||......#|#..##...|#....#....|#|.#.
+.##.|.##|.#.||....#|....|.#.|#.|....##..#.##|.....
+|...|...#|....#....#...#|#...|..#.#.|.|.....|.#|..
+.|.|.#.#.#|.#.|#....|.|###..#......|...|...#.|#...
+..|...||.|..##|...|..|#|...|......#.||.#...#..|#.|
+........|..#||..|....|.....|.|#..#....|#..|.#.....
+#.|.|#....#...|..|....|.#.....||.....|..|........#
+...||||....|.#.|....#..#....|###....|...#...##....
+|||........|.#|.|......||#.|.....|.||#|.##....#|..
+.....|#|#..||#...|##.|..||....####.|#.|..#....|.#.
+.||..#||....#.....#.#|.|....|.##|..|.#..|##....##.
+.|#.#|#|#|.....||..|.|.|.#......#..|.#..#..|.#||#.
+|.|#.......|..#|#|....|.#.#.#.|...|.......##.|||#|
+..|.....#...||.|....|##|...#..#.#.....|##|##.##...
+.|.|..##.#|..|.|#.......#....#||.|...||#...|......
+|.|##.#....|#..|....#..#..|##.|.##..#......#|##|..
+..#....#.|#...#.#...|.....|.||.#.#|.#.|###..|..#.#
+..|.##...........|..###.||.|.##.|....|.|.#|#.#.|#|
+..|....|.|#|...#|#...|.#......#.#||...|.#|...#.|#.
+..#.......|.||.....||.|....|#||..........#...|#...
+.|..#....|#|||#..##||..#|.......|..|###..|.#...|.|
+|..|.#|.#...#....|.....#.....#....#...|..|.|.#.|.#
+....###.#....|.#..#...#...###.|.|.....#|...#.....|
+..#....##.....##..|.#.||#.|.#|#||..|...#|..|.#....
+|#..#.#|||#.|#..#........#......||...#.|..#|....#|
+......#|...#.|...#...|.|...|#|#......#|.##.#|.|.#|
+#||.#......#.##......#..||.##|.|.||..|#....#..#...
+#.#...#.|.#|#||#.#......#....|##|.........##.#|...
+.....###...#||....|####..#|||...#..#|.|....#|..#..
+......|#..#.#.#..|.#|#||..||.|...#....##...|......
+...#...|..#..##.||.#.#.....|.###.....##|#||..#..#|
+.#..#||.#....||....|##..|||...|.||...#..##.#....#.