Day17

days/src/main/kotlin/Day17.kt

@@ -0,0 +1,127 @@
+package be.vandewalleh.aoc.days
+
+import be.vandewalleh.aoc.utils.input.Day
+import be.vandewalleh.aoc.utils.input.Input
+import be.vandewalleh.aoc.utils.input.Lines
+import be.vandewalleh.aoc.utils.input.createDay
+
+data class Point(val x: Int, val y: Int, val z: Int)
+
+data class Point4(val x: Int, val y: Int, val z: Int, val blah: Int)
+
+enum class State { Active, Inactive }
+
+@Day(17)
+class Day17(@Lines val input: Input<List<String>>) {
+
+    private fun neighbours3(point: Point): List<Point> {
+        val points = mutableListOf<Point>()
+        for (x in point.x - 1..point.x + 1) {
+            for (y in point.y - 1..point.y + 1) {
+                for (z in point.z - 1..point.z + 1) {
+                    val generatedPoint = Point(x, y, z)
+                    if (generatedPoint != point)
+                        points.add(generatedPoint)
+                }
+            }
+        }
+        check(points.size == 26) { "Points size was ${points.size}" }
+        return points
+    }
+
+    private fun neighbours4(point: Point4): List<Point4> {
+        val points = mutableListOf<Point4>()
+        for (x in point.x - 1..point.x + 1) {
+            for (y in point.y - 1..point.y + 1) {
+                for (z in point.z - 1..point.z + 1) {
+                    for (blah in point.blah - 1..point.blah + 1) {
+                        val generatedPoint = Point4(x, y, z, blah)
+                        if (generatedPoint != point)
+                            points.add(generatedPoint)
+                    }
+                }
+            }
+        }
+        check(points.size == 80) { "Points size was ${points.size}" }
+        return points
+    }
+
+    fun part1(): Int {
+        val grid = parseGrid3()
+        repeat(6) { step3(grid) }
+        return grid.values.count { it == State.Active }
+    }
+
+    private fun parseGrid3(): MutableMap<Point, State> {
+        val grid = mutableMapOf<Point, State>()
+        input.value.forEachIndexed { index, row ->
+            row.forEachIndexed { col, char ->
+                val state = if (char == '#') State.Active else State.Inactive
+                grid[Point(index, col, 0)] = state
+            }
+        }
+        return grid
+    }
+
+    private fun parseGrid4(): MutableMap<Point4, State> {
+        val grid = mutableMapOf<Point4, State>()
+        input.value.forEachIndexed { index, row ->
+            row.forEachIndexed { col, char ->
+                val state = if (char == '#') State.Active else State.Inactive
+                grid[Point4(index, col, 0, 0)] = state
+            }
+        }
+        return grid
+    }
+
+    private fun step3(grid: MutableMap<Point, State>) {
+        val pointsToConsider = grid.keys.flatMap { neighbours3(it) }.toSet()
+
+        val modifications = mutableMapOf<Point, State>()
+        for (point in pointsToConsider) {
+            val neighbours = neighbours3(point)
+            val activeNeighboursCount = neighbours.count { grid[it] ?: State.Inactive == State.Active }
+            val state = grid[point] ?: State.Inactive
+            if (state == State.Active && activeNeighboursCount !in 2..3) {
+                modifications[point] = State.Inactive
+            } else if (activeNeighboursCount == 3) {
+                modifications[point] = State.Active
+            }
+        }
+        for ((point, state) in modifications) {
+            grid[point] = state
+        }
+    }
+
+    private fun step4(grid: MutableMap<Point4, State>) {
+        val pointsToConsider = grid.keys.flatMap { neighbours4(it) }.toSet()
+
+        val modifications = mutableMapOf<Point4, State>()
+        for (point in pointsToConsider) {
+            val neighbours = neighbours4(point)
+            val activeNeighboursCount = neighbours.count { grid[it] ?: State.Inactive == State.Active }
+            val state = grid[point] ?: State.Inactive
+            if (state == State.Active && activeNeighboursCount !in 2..3) {
+                modifications[point] = State.Inactive
+            } else if (activeNeighboursCount == 3) {
+                modifications[point] = State.Active
+            }
+        }
+        for ((point, state) in modifications) {
+            grid[point] = state
+        }
+    }
+
+    fun part2(): Int {
+        val grid = parseGrid4()
+        repeat(6) { step4(grid) }
+        return grid.values.count { it == State.Active }
+    }
+
+}
+
+fun main() = with(createDay<Day17>(
+)) {
+    println(part1())
+    println(part2())
+}

days/src/main/resources/day17.txt

@@ -0,0 +1,8 @@
+##..#.#.
+#####.##
+#######.
+#..#..#.
+#.#...##
+..#....#
+....#..#
+..##.#..