44 lines
1.2 KiB
Kotlin
44 lines
1.2 KiB
Kotlin
import java.io.File
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import kotlin.text.Regex
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fun main() {
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val input = File("input")
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val races = parseRaces(input)
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println(part1(races))
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val singleRace = parseSingleRace(input)
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println(part1(listOf(singleRace)))
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}
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fun part1(races: List<Pair<Long, Long>>): Long {
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return races.map { getNumberOfWins(it.first, it.second) }.reduce { count, acc -> count * acc }
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}
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fun getNumberOfWins(time: Long, distance: Long): Long {
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val wins = (0..time / 2).filter { it * (time - it) > distance }.count()
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return when (time % 2) {
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0L -> (wins - 1L) * 2L + 1L
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1L -> wins * 2L
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else -> throw Exception("Unreachable")
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}
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}
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fun parseSingleRace(input: File): Pair<Long, Long> {
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return input.useLines {
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val numbers =
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it
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.map { it.split(':').drop(1).single().filter { it.isDigit() }.toLong() }
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.iterator()
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Pair(numbers.next(), numbers.next())
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}
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}
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fun parseRaces(input: File): List<Pair<Long, Long>> {
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return input.useLines {
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val numbers = it.map { it.split(Regex("\\s+")).drop(1).map { it.toLong() } }.iterator()
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numbers.next().zip(numbers.next()).map { (time, distance) -> Pair(time, distance) }
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}
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}
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