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Solution 2018-04 (Repose Record)
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‎src/main/kotlin/de/ronny_h/aoc/year2018/day04/ReposeRecord.kt‎

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package de.ronny_h.aoc.year2018.day04
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import de.ronny_h.aoc.AdventOfCode
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import de.ronny_h.aoc.year2018.day04.GuardEvent.*
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fun main() = ReposeRecord().run(140932, 51232)
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class ReposeRecord : AdventOfCode<Int>(2018, 4) {
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override fun part1(input: List<String>): Int {
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val guardDutyRecords = input.parseRecords()
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val guardWithMaxSleep = guardDutyRecords.findGuardWithMostSleep()
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println("the guard with max sleep minutes: $guardWithMaxSleep")
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val maxSleepMinute = guardDutyRecords
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.filter { it.guardId == guardWithMaxSleep.guardId }
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.findMinuteAsleepMostFrequently()
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println("the guard was asleep most during minute: $maxSleepMinute}")
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return guardWithMaxSleep.guardId * maxSleepMinute.minute
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}
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override fun part2(input: List<String>): Int {
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input.parseRecords()
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.groupBy { it.guardId }
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.filter {
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// there are actually guards that don't fall asleep at all
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it.value.any { record -> record.event == FALL_ASLEEP }
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}
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.map { it.key to it.value.findMinuteAsleepMostFrequently() }
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.maxBy { it.second.sleepCount }
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.let { return it.first * it.second.minute }
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}
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private fun List<GuardDutyRecord>.findGuardWithMostSleep(): GuardSleepMinutes {
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val sleepMinutes = mutableMapOf<Int, Int>().withDefault { 0 }
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var guardId: Int = -1
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var fallAsleepAt: Int = -1
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forEach {
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when (it.event) {
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BEGIN_SHIFT -> guardId = it.guardId
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FALL_ASLEEP -> fallAsleepAt = it.minute()
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WAKE_UP -> sleepMinutes[guardId] = sleepMinutes.getValue(guardId) + it.minute() - fallAsleepAt
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}
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}
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return sleepMinutes
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.maxBy { it.value }
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.let { GuardSleepMinutes(it.key, it.value) }
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}
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private fun List<GuardDutyRecord>.findMinuteAsleepMostFrequently(): SleepPerMinute {
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val asleepPerMinute = mutableMapOf<Int, Int>().withDefault { 0 }
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var fallAsleepAt: Int = -1
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forEach {
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when (it.event) {
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FALL_ASLEEP -> fallAsleepAt = it.minute()
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WAKE_UP -> {
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for (minute in fallAsleepAt..<it.minute()) {
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asleepPerMinute[minute] = asleepPerMinute.getValue(minute) + 1
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}
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}
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else -> {} // noting to do
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}
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}
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return asleepPerMinute.maxBy { it.value }.let { SleepPerMinute(it.key, it.value) }
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}
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}
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// records have the form:
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// [1518-11-01 00:00] Guard #10 begins shift
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// [1518-11-01 00:05] falls asleep
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// [1518-11-01 00:25] wakes up
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fun List<String>.parseRecords(): List<GuardDutyRecord> {
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var guardId = -1
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return map {
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val (time, event) = it.substringAfter("[").split("] ")
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time to event
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}
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.sortedBy { it.first }
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.map {
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when (it.second) {
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"falls asleep" -> GuardDutyRecord(it.first, guardId, FALL_ASLEEP)
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"wakes up" -> GuardDutyRecord(it.first, guardId, WAKE_UP)
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else -> {
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guardId = it.second.substringAfter("Guard #").substringBefore(" begins shift").toInt()
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GuardDutyRecord(it.first, guardId, BEGIN_SHIFT)
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}
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}
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}
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}
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data class GuardDutyRecord(private val time: String, val guardId: Int, val event: GuardEvent) {
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fun minute(): Int = time.split(":")[1].toInt()
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}
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enum class GuardEvent { BEGIN_SHIFT, FALL_ASLEEP, WAKE_UP }
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data class GuardSleepMinutes(val guardId: Int, val minutes: Int)
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data class SleepPerMinute(val minute: Int, val sleepCount: Int)

‎src/test/kotlin/de/ronny_h/aoc/year2018/day04/ReposeRecordTest.kt‎

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package de.ronny_h.aoc.year2018.day04
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import de.ronny_h.aoc.extensions.asList
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import de.ronny_h.aoc.year2018.day04.GuardEvent.*
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import io.kotest.core.spec.style.StringSpec
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import io.kotest.matchers.shouldBe
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class ReposeRecordTest : StringSpec({
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val input = """
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[1518-11-01 00:00] Guard #10 begins shift
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[1518-11-01 00:05] falls asleep
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[1518-11-01 00:25] wakes up
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[1518-11-01 00:30] falls asleep
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[1518-11-01 00:55] wakes up
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[1518-11-01 23:58] Guard #99 begins shift
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[1518-11-02 00:40] falls asleep
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[1518-11-02 00:50] wakes up
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[1518-11-03 00:05] Guard #10 begins shift
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[1518-11-03 00:24] falls asleep
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[1518-11-03 00:29] wakes up
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[1518-11-04 00:02] Guard #99 begins shift
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[1518-11-04 00:36] falls asleep
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[1518-11-04 00:46] wakes up
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[1518-11-05 00:03] Guard #99 begins shift
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[1518-11-05 00:45] falls asleep
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[1518-11-05 00:55] wakes up
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""".asList()
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"input can be parsed" {
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input.parseRecords() shouldBe listOf(
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GuardDutyRecord("1518-11-01 00:00", 10, BEGIN_SHIFT),
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GuardDutyRecord("1518-11-01 00:05", 10, FALL_ASLEEP),
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GuardDutyRecord("1518-11-01 00:25", 10, WAKE_UP),
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GuardDutyRecord("1518-11-01 00:30", 10, FALL_ASLEEP),
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GuardDutyRecord("1518-11-01 00:55", 10, WAKE_UP),
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GuardDutyRecord("1518-11-01 23:58", 99, BEGIN_SHIFT),
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GuardDutyRecord("1518-11-02 00:40", 99, FALL_ASLEEP),
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GuardDutyRecord("1518-11-02 00:50", 99, WAKE_UP),
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GuardDutyRecord("1518-11-03 00:05", 10, BEGIN_SHIFT),
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GuardDutyRecord("1518-11-03 00:24", 10, FALL_ASLEEP),
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GuardDutyRecord("1518-11-03 00:29", 10, WAKE_UP),
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GuardDutyRecord("1518-11-04 00:02", 99, BEGIN_SHIFT),
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GuardDutyRecord("1518-11-04 00:36", 99, FALL_ASLEEP),
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GuardDutyRecord("1518-11-04 00:46", 99, WAKE_UP),
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GuardDutyRecord("1518-11-05 00:03", 99, BEGIN_SHIFT),
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GuardDutyRecord("1518-11-05 00:45", 99, FALL_ASLEEP),
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GuardDutyRecord("1518-11-05 00:55", 99, WAKE_UP),
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)
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}
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"input gets sorted by timestamp" {
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"""
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[1518-11-01 00:25] wakes up
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[1518-11-01 00:05] falls asleep
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[1518-11-01 00:00] Guard #10 begins shift
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[1518-11-01 00:30] falls asleep
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""".asList()
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.parseRecords() shouldBe listOf(
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GuardDutyRecord("1518-11-01 00:00", 10, BEGIN_SHIFT),
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GuardDutyRecord("1518-11-01 00:05", 10, FALL_ASLEEP),
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GuardDutyRecord("1518-11-01 00:25", 10, WAKE_UP),
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GuardDutyRecord("1518-11-01 00:30", 10, FALL_ASLEEP),
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)
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}
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"part 1: the guard's id who slept most, multiplied by the minute he slept most" {
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ReposeRecord().part1(input) shouldBe 240
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}
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"part 2: the guard's id who sleeps most frequently in the same minute, multiplied by that minute" {
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ReposeRecord().part2(input) shouldBe 4455
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}
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})

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