Day 14

Author: Nxllpointer

build.gradle.kts

@@ -7,7 +7,7 @@ plugins {
 group = "de.nxll.aoc2022"
 version = "1.0"
 
-val currentDay = 13
+val currentDay = 14
 
 repositories {
  mavenCentral()

src/day_14/kotlin/Day14.kt

@@ -0,0 +1,124 @@
+import kotlin.math.sign
+
+// AOC Day 14
+
+const val rockCharacter = '#'
+const val sandCharacter = '.'
+const val airCharacter = ' '
+const val printCave = false
+
+typealias Cave = Array<CharArray>
+
+fun Cave.print() = forEach { println(it.joinToString(" ")) }.also { println() }
+operator fun Cave.get(point: Vector2D) = this[point.y][point.x]
+operator fun Cave.set(point: Vector2D, char: Char) {
+ this[point.y][point.x] = char
+}
+
+val sandMovesPriorityOrdered = listOf(Vector2D(0, 1), Vector2D(-1, 1), Vector2D(1, 1))
+fun Cave.simulateFallingSand(startPosition: Vector2D): Vector2D {
+ var currentPosition = startPosition
+ var isResting = false
+
+ while (!isResting) {
+ sandMovesPriorityOrdered
+ .map { currentPosition + it }
+ .filter { it.y in 0..this.lastIndex && it.x in 0..this[0].lastIndex }
+ .filter { this[it] == airCharacter }
+ .apply {
+ if (none()) isResting = true
+ else currentPosition = first()
+ }
+ }
+
+ return currentPosition
+}
+
+fun part1(cave: Cave, sandSourcePoint: Vector2D) {
+ var sandUnits = 0
+ while (true) {
+ val sandRestingPoint = cave.simulateFallingSand(sandSourcePoint)
+ if (sandRestingPoint.y == cave.lastIndex - 1) break
+ sandUnits++
+ cave[sandRestingPoint] = sandCharacter
+ }
+
+ if (printCave) cave.print()
+ println("Part 1: The first unit of sand falls into the abyss after $sandUnits sand units have come to rest")
+}
+
+fun part2(cave: Cave, sandSourcePoint: Vector2D) {
+ var sandUnits = 0
+ while (true) {
+ val sandRestingPoint = cave.simulateFallingSand(sandSourcePoint)
+ sandUnits++
+ cave[sandRestingPoint] = sandCharacter
+ if (sandRestingPoint == sandSourcePoint) break
+ }
+
+ if (printCave) cave.print()
+ println("Part 2: $sandUnits sand untis have to come to rest for the source to be blocked")
+}
+
+fun String.toPoint() = this.split(",").mapToInt().run { Vector2D(first(), last()) }
+fun Cave.deepCopy(): Cave = map { it.toList().toCharArray() }.toTypedArray()
+val pointRegex = "\\d+,\\d+".toRegex()
+
+fun main() {
+ val (cave, sandSourcePoint) = getAOCInput { rawInput ->
+ val points = pointRegex.findAll(rawInput).map { it.value.toPoint() }
+
+ var minX = points.minOf { it.x }
+ var maxX = points.maxOf { it.x }
+ val minY = 0 // Sand level
+ var maxY = points.maxOf { it.y }
+
+
+ val floorHeight = maxY + 2
+ maxY = floorHeight
+ minX -= floorHeight
+ maxX += floorHeight
+
+ fun Vector2D.asNormalized() = Vector2D(x - minX, y - minY)
+
+ val cave: Cave = Array(maxY - minY + 1) { CharArray(maxX - minX + 1) { airCharacter } }
+
+ val sandSourcePoint = Vector2D(500, 0).asNormalized()
+ cave[sandSourcePoint] = 'S'
+
+ val floorPath = Vector2D(minX, floorHeight).asNormalized() to Vector2D(maxX, floorHeight).asNormalized()
+
+ val paths = rawInput.trim().lines()
+ .flatMap { line ->
+ line
+ .split(" -> ")
+ .map { it.toPoint().asNormalized() }
+ .zipWithNext()
+ }
+ .plus(floorPath)
+
+ paths.forEach { (start, end) ->
+ var currentPos = start
+
+ val signX = (end.x - start.x).sign
+ val signY = (end.y - start.y).sign
+
+ while (currentPos.x != end.x) {
+ cave[currentPos] = rockCharacter
+ currentPos += Vector2D(signX, 0)
+ cave[currentPos] = rockCharacter
+ }
+
+ while (currentPos.y != end.y) {
+ cave[currentPos] = rockCharacter
+ currentPos += Vector2D(0, signY)
+ cave[currentPos] = rockCharacter
+ }
+ }
+
+ cave to sandSourcePoint
+ }
+
+ part1(cave.deepCopy(), sandSourcePoint)
+ part2(cave.deepCopy(), sandSourcePoint)
+}