93 lines
3.1 KiB
Kotlin
93 lines
3.1 KiB
Kotlin
package aoc2023
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import println
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import readInput
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/*
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--- Day 12: Hot Springs ---
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https://adventofcode.com/2023/day/12
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*/
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fun main() {
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val inlineTestInput = """
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???.### 1,1,3
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.??..??...?##. 1,1,3
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?#?#?#?#?#?#?#? 1,3,1,6
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????.#...#... 4,1,1
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????.######..#####. 1,6,5
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?###???????? 3,2,1
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"""
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val memo = HashMap<Int, Long>()
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fun fits(input: String, regs: IntArray, inputPos: Int, regPos: Int): Boolean {
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if (regPos > regs.lastIndex || inputPos + regs[regPos] > input.length) return false
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var ip = inputPos
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var e = regs[regPos]
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if (input[ip] == '.') ip++
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while ((e > 0) && ip <= input.lastIndex && input[ip++] != '.') {
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e--
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}
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if (e > 0) return false
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return ip > input.lastIndex || input[ip] != '#'
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}
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fun count(input: String, regs: IntArray, inputPos: Int, regPos: Int): Long {
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val memVal = memo[inputPos * 1000 + regPos]
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if (memVal != null) return memVal
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//println("$inputPos, $regPos, ${input.substring(inputPos)}")
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if (inputPos > input.lastIndex && regPos > regs.lastIndex) return 1
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if (inputPos > input.lastIndex) return 0
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var result = 0L
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if (input[inputPos] != '#') {
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result += count(input, regs, inputPos + 1, regPos).also { memo[(inputPos + 1) * 1000 + regPos] = it }
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}
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if (input[inputPos] != '.') {
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if (fits(input, regs, inputPos, regPos)) {
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val p = inputPos + regs[regPos] + 1
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result += count(input, regs, p, regPos + 1).also { memo[p * 1000 + regPos + 1] = it }
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}
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}
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return result
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}
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fun part1(input: List<String>): Long {
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val results = input.map {
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val (springline, parms) = it.split(" ")
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val reduced = springline.replace("\\.+".toRegex(), ".").trim { it == '.' }
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val regs = parms.split(",").map { it.toInt() }.toIntArray()
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memo.clear()
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count(reduced, regs, 0, 0)
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}
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return results.sum()
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}
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fun part2(input: List<String>): Long {
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val results = input.map {
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val (springline, parms) = it.split(" ")
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val reduced = springline.replace("\\.+".toRegex(), ".")
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val regs = parms.split(",").map { it.toInt() }.toList()
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val regs5 = List(5) { regs }.flatten().toIntArray()
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val red5 = List(5) { reduced }.joinToString("?").trim { it == '.' }
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memo.clear()
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count(red5, regs5, 0, 0)
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}
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return results.sum()
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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("aoc2023/Day12_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 == 21L)
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check(testInputPart2Result == 525152L)
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val input = readInput("aoc2023/Day12")
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part1(input).println()
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part2(input).println()
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}
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