118 lines
3.8 KiB
Kotlin
118 lines
3.8 KiB
Kotlin
package aoc2024
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import println
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import readInput
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/*
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--- Day 9: Disk Fragmenter ---
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https://adventofcode.com/2024/day/9
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*/
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fun main() {
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val inlineTestInput = """2333133121414131402"""
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fun part1(input: List<String>): Long {
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val diskSize = input[0].sumOf { it - '0' }
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val bitmap = IntArray(diskSize) { -1 }
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var pos = 0
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var isFile = true
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var fileId = 0
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var usedBlocks = 0
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for (c in input[0]) {
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val size = c - '0'
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if (isFile) {
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usedBlocks += size
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for (p in 1..size) {
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bitmap[pos++] = fileId
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}
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fileId++
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} else {
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pos += size
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}
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isFile = !isFile
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}
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var backPos = diskSize - 1
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for (i in 0 until usedBlocks) {
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if (bitmap[i] == -1) {
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while (bitmap[backPos] < 0) {
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backPos--
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}
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bitmap[i] = bitmap[backPos]
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bitmap[backPos--] = -1
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}
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}
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return bitmap.take(usedBlocks).map(Int::toLong).reduceIndexed { index, acc, i -> acc + index * i }
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}
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fun part2(input: List<String>): Long {
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val diskSize = input[0].sumOf { it - '0' }
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val bitmap = IntArray(diskSize) { 0 }
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var pos = 0
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var isFile = true
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var fileId = 0
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val freeList = HashMap<Int, MutableList<Int>>()
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val fileList = ArrayList<Pair<Int, Pair<Int, Int>>>()
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val newFileList = ArrayList<Pair<Int, Pair<Int, Int>>>()
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for (c in input[0]) {
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val size = c - '0'
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if (isFile) {
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if (size == 0) println("Narf!")
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fileList.add(fileId to (pos to size))
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fileId++
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} else {
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if (size > 0) {
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freeList.getOrPut(size) { ArrayDeque(0) }.add(pos)
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}
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}
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pos += size
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isFile = !isFile
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}
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for (file in fileList.reversed()) {
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val (filePos, size) = file.second
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var bestList: MutableList<Int>? = null
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var bestListSize = 0
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for (s in size..9) {
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val list = freeList[s]
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if (list?.isNotEmpty() == true && list[0] < filePos) {
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if (bestList == null || list[0] < bestList[0]) {
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bestList = list
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bestListSize = s
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}
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}
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}
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if (bestList != null) {
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val newPos = bestList.removeAt(0)
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if (bestListSize > size) {
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val remBucket = freeList.getOrPut(bestListSize - size) { ArrayDeque(0) }
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remBucket.add(newPos + size)
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remBucket.sort()
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}
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newFileList.add(file.first to (newPos to size))
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} else {
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newFileList.add(file)
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}
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}
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for (file in newFileList) {
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for (i in 0 until file.second.second) {
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bitmap[i + file.second.first] = file.first
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}
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}
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return bitmap.map(Int::toLong).reduceIndexed { index, acc, i -> acc + index * i }
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}
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// test if implementation meets criteria from the description, like:
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val testInput = inlineTestInput.trim().reader().readLines()
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//val testInput = readInput("aoc2024/Day09_test")
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val testInputPart1Result = part1(testInput)
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println("Part 1 Test: $testInputPart1Result")
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val testInputPart2Result = part2(testInput)
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println("Part 2 Test: $testInputPart2Result")
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check(testInputPart1Result == 1928L)
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check(testInputPart2Result == 2858L)
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val input = readInput("aoc2024/Day09")
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part1(input).println()
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part2(input).println()
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}
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