55 lines
1.3 KiB
Kotlin
55 lines
1.3 KiB
Kotlin
import java.io.File
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import java.math.BigInteger
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import kotlin.system.measureTimeMillis
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fun main() {
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val initialConfiguration = File("input.txt").readLines()
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.single()
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.split(',')
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.map(String::toInt)
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println("(Took ${measureTimeMillis { part1(initialConfiguration) }} ms)")
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println("(Took ${measureTimeMillis { part2(initialConfiguration) }} ms)")
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}
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class FishConfiguration(initialConfiguration: List<Int>) {
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private var fishCountByAge = Array(9) { age -> initialConfiguration.count { it == age }.toBigInteger() }
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private var day = 0
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private val totalFish
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get() = fishCountByAge.fold(BigInteger.ZERO, BigInteger::add)
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fun advance(days: Int) {
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for (day in 1..days) {
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advanceToNextDay()
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}
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}
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private fun advanceToNextDay() {
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val newCountByAge = Array(9) { BigInteger.ZERO}
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for ((age, count) in fishCountByAge.withIndex()) {
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if (age == 0) {
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newCountByAge[6] += count
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newCountByAge[8] += count
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}
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else {
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newCountByAge[age - 1] += count
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}
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}
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fishCountByAge = newCountByAge
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++day
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println("Day ${day.toString().padStart(3)}: $totalFish fish")
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}
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}
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fun part1(initialConfiguration: List<Int>) {
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FishConfiguration(initialConfiguration).advance(80)
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}
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fun part2(initialConfiguration: List<Int>) {
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FishConfiguration(initialConfiguration).advance(256)
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}
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