aoc-2024 - Day 15 - part 1

Author: Krystian Kaniowski

advent-of-code-2024/src/Day10.kt

@@ -41,7 +41,7 @@ fun main() {
 
  val array = Array2d.readNumbers(input)
 
- return array.getPositions(9)
+ return array.findAll { it == 9 }
  .sumOf {
  goDown(array, listOf(it), 9, it.x, it.y)
  .filterNotNull()
@@ -55,7 +55,7 @@ fun main() {
 
  val array = Array2d.readNumbers(input)
 
- return array.getPositions(0)
+ return array.findAll { it == 0 }
  .sumOf {
  goUp(array, listOf(it), 0, it.x, it.y)
  .filterNotNull()

advent-of-code-2024/src/Day15.kt

@@ -0,0 +1,66 @@
+import util.Array2d
+import util.Vector
+
+// https://adventofcode.com/2024/day/15
+fun main() {
+
+ val INSTRUTCION_MAPPING = mapOf(
+ '>' to Vector.RIGHT,
+ '<' to Vector.LEFT,
+ '^' to Vector.UP,
+ 'v' to Vector.DOWN,
+ )
+
+ val WALL = '#'
+ val EMPTY = '.'
+ val MACHINE = '@'
+ val BOX = 'O'
+ val BOX_2_LEFT = '['
+ val BOX_2_RIGHT = ']'
+
+ fun Vector.isVertical() = this in listOf(Vector.UP, Vector.DOWN)
+
+ fun part1(input: List<String>): Int {
+
+ val map = Array2d.readChar(input.filter { it.contains(WALL) })
+ val instructions = input.filter { it.any { it in INSTRUTCION_MAPPING.keys } }
+ .flatMap { it.toList() }
+ .mapNotNull { INSTRUTCION_MAPPING[it] }
+
+ var position = map.findAny { it == MACHINE }!!
+
+ instructions.forEach { vector ->
+ var head = position
+ val snake = mutableListOf(head)
+ while (map[head + vector] == BOX) {
+ head += vector
+ snake.add(head)
+ }
+ if (map[head + vector] == EMPTY) {
+ snake.reversed().forEachIndexed { index, point ->
+ map[point + vector] = map[point]
+ if (index == snake.size - 1) {
+ position = point + vector
+ map[point] = EMPTY
+ }
+ }
+ }
+ }
+
+ val boxes = map.findAll { it == BOX }
+
+ return boxes.sumOf { 100 * it.y + it.x }
+ }
+
+ fun part2(input: List<String>): Int {
+ return TODO()
+ }
+
+ val testInput = readInput("Day15_test")
+ val input = readInput("Day15")
+
+ test(10092) { part1(testInput) }
+ exec { part1(input) }
+ test(9021) { part2(testInput) }
+ exec { part2(input) }
+}

advent-of-code-2024/src/util/Array2d.kt

@@ -8,53 +8,64 @@ class Array2d<Type>(
 
  private val array: MutableList<MutableList<Type>> = MutableList(height) { MutableList(width) { defaultValue } }
 
+ operator fun get(point: Point) = get(point.x, point.y)
  operator fun get(x: Int, y: Int): Type = array[y][x]
+
+ fun getSafe(point: Point) = getSafe(point.x, point.y)
+ fun getSafe(x: Int, y: Int) = if (isInBounds(x, y)) array[y][x] else null
+
+ operator fun set(point: Point, value: Type) = set(point.x, point.y, value)
  operator fun set(x: Int, y: Int, value: Type) {
  array[y][x] = value
  }
 
- operator fun set(point: Point, value: Type) = set(point.x, point.y, value)
-
- operator fun get(point: Point) = get(point.x, point.y)
-
  fun setSafe(point: Point, value: Type) = setSafe(point.x, point.y, value)
  fun setSafe(x: Int, y: Int, value: Type) {
  if (isInBounds(x, y)) array[y][x] = value
  }
 
- fun getSafe(point: Point) = getSafe(point.x, point.y)
- fun getSafe(x: Int, y: Int) = if (isInBounds(x, y)) array[y][x] else null
+ fun isInBounds(point: Point) = isInBounds(point.x, point.y)
+ fun isInBounds(x: Int, y: Int) = x in 0 until width && y in 0 until height
 
- fun forEach(action: (x: Int, y: Int, value: Type) -> Unit) {
+ fun findAny(filter: (Type) -> Boolean): Point? {
  for (y in array.indices) {
  for (x in array[y].indices) {
- action(x, y, array[y][x])
+ if (filter(array[y][x])) return Point(x, y)
  }
  }
+ return null
  }
 
- fun getPositions(value: Type): List<Point> {
- return array.mapIndexed { y, list -> list.mapIndexed { x, v -> if (v == value) Point(x, y) else null } }
- .flatten()
- .filterNotNull()
+ fun findAll(filter: (Type) -> Boolean): List<Point> {
+ val findings = mutableListOf<Point>()
+ for (y in array.indices) {
+ for (x in array[y].indices) {
+ if (filter(array[y][x])) findings.add(Point(x, y))
+ }
+ }
+ return findings
  }
 
- fun isInBounds(point: Point) = isInBounds(point.x, point.y)
+ fun forEach(action: (x: Int, y: Int, value: Type) -> Unit) {
+ for (y in array.indices) {
+ for (x in array[y].indices) {
+ action(x, y, array[y][x])
+ }
+ }
+ }
 
- fun isInBounds(x: Int, y: Int) = x in 0 until width && y in 0 until height
+ fun count(filter: (Type) -> Boolean): Int = array.sumOf { it.count { filter(it) } }
 
  fun createMask(): Array2d<Boolean> = Array2d(width, height, false)
 
- fun count(filter: (Type) -> Boolean): Int = array.sumOf { it.count { filter(it) } }
-
  fun print(mapper: (Type) -> Char) {
  for (y in array.indices) {
  for (x in array[y].indices) {
- print(mapper(array[x][y]))
+ print(mapper(array[y][x]))
  }
- println("")
+ println()
  }
- println("")
+ println()
  }
 
  companion object {

advent-of-code-2024/src/util/Point.kt

@@ -3,6 +3,7 @@ package util
 data class Point(val x: Int, val y: Int) {
 
  operator fun plus(vector: Vector) = Point(x + vector.x, y + vector.y)
+ operator fun minus(vector: Vector) = Point(x - vector.x, y - vector.y)
 
  override fun toString(): String {
  return "[$x, $y]"