Day 13

Author: Kanialdo

src/day13/Day13.kt

@@ -0,0 +1,112 @@
+package day13
+
+import utils.verify
+import java.io.File
+
+/** https://adventofcode.com/2021/day/13 */
+
+fun main() {
+
+ data class Fold(val x: Boolean, val pos: Int)
+
+ class Data(lines: List<String>) {
+ private val matrix: Array<BooleanArray>
+ private val folds: ArrayDeque<Fold>
+
+ private var maxX: Int
+ private var maxY: Int
+
+ init {
+ val _folds: MutableList<Fold> = mutableListOf()
+ val list: MutableList<Pair<Int, Int>> = mutableListOf()
+ lines.forEach { line ->
+ when {
+ line.startsWith("fold") -> line.replace("fold along ", "").split("=")
+ .let { _folds.add(Fold(it[0] == "x", it[1].toInt())) }
+ line.isBlank() -> {}
+ else -> line.split(",").map(String::toInt).let { list.add(it[0] to it[1]) }
+ }
+ }
+ folds = ArrayDeque(_folds)
+ maxX = list.maxOf { it.first + 1 }
+ maxY = list.maxOf { it.second + 1 }
+ matrix = Array(maxY) { BooleanArray(maxX) }
+ list.forEach { matrix[it.second][it.first] = true }
+ }
+
+ fun fold(limit: Int = Int.MAX_VALUE) {
+ var counter = 0
+ do {
+ val fold = folds.removeFirstOrNull() ?: return
+ if (fold.x) {
+ for (x in 0 until fold.pos) {
+ for (y in 0 until maxY) {
+ matrix[y][x] = matrix[y][x] || matrix[y][maxX - x - 1]
+ }
+ }
+ maxX = fold.pos
+ } else {
+ for (x in 0 until maxX) {
+ for (y in 0 until fold.pos) {
+ matrix[y][x] = matrix[y][x] || matrix[maxY - y - 1][x]
+ }
+ }
+ maxY = fold.pos
+ }
+ counter++
+ if (counter == limit) {
+ return
+ }
+ } while (true)
+ }
+
+ fun print() {
+ println()
+ for (y in 0 until maxY) {
+ for (x in 0 until maxX) {
+ print(if (matrix[y][x]) "#" else ".")
+ }
+ println()
+ }
+ }
+
+ fun count(): Int {
+ var result = 0
+ for (y in 0 until maxY) {
+ for (x in 0 until maxX) {
+ if (matrix[y][x]) {
+ result++
+ }
+ }
+ }
+ return result
+ }
+ }
+
+ fun File.read() = Data(readLines())
+
+ fun part1(data: Data): Int {
+ // data.print()
+ data.fold(1)
+ // data.print()
+ return data.count()
+ }
+
+
+ fun part2(data: Data): Int {
+ data.fold()
+ data.print()
+ return 0
+ }
+
+ // ---- RUN
+
+ val testData = File("src/day13/input_test.txt").read()
+ val data = File("src/day13/input.txt").read()
+
+ verify(17, part1(testData))
+ verify(647, part1(data))
+
+ verify(0, part2(testData)) // result 0
+ verify(0, part2(data)) // result HEJHJRCJ
+}