54 lines
1.3 KiB
Kotlin
54 lines
1.3 KiB
Kotlin
package be.vandewalleh.aoc.days
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import be.vandewalleh.aoc.utils.input.Csv
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import be.vandewalleh.aoc.utils.input.Day
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import be.vandewalleh.aoc.utils.input.Input
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import be.vandewalleh.aoc.utils.input.createDay
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import kotlin.math.abs
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import org.eclipse.collections.impl.factory.primitive.IntObjectMaps
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@Day(15)
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class Day15(@Csv val input: Input<IntArray>) {
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private fun run(until: Int): Int {
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val start = input.value
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val map = IntObjectMaps.mutable.empty<IntArray>()
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var last = -1
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fun say(round: Int, number: Int) {
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val lastValues = map.get(number)
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val values = lastValues
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?.let { intArrayOf(round, it.maxOrNull()!!) }
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?: intArrayOf(round)
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map.put(number, values)
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last = number
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}
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for (i in 1..until) {
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if (i <= start.size) {
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say(i, start[i - 1])
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} else {
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val lastValues = map.get(last)
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if (lastValues?.size ?: 0 < 2) say(i, 0)
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else say(i, abs(lastValues[0] - lastValues[1]))
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}
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}
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return last
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}
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fun part1() = run(until = 2020)
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fun part2() = run(until = 30000000)
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}
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fun main() {
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// val input = Input(intArrayOf(3, 1, 2))
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with(createDay<Day15>()) {
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println(part1())
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println(part2())
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}
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}
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