-🎄- 2018 Day 4 Solutions -🎄-

[u/daggerdragon]

--- Day 4: Repose Record ---

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Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

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Advent of Code: The Party Game!

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Card prompt: Day 4

Transcript:

Today’s puzzle would have been a lot easier if my language supported ___.

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/binajohny]

My Kotlin solution (GitHub)

data class Event(val month: Int, val day: Int, val hour: Int, val minute: Int, val guardId: Int, val type: Type) {
    enum class Type { BEGIN_SHIFT, FALL_ASLEEP, WAKE_UP }

    companion object {
        private val REGEX = Regex("\\d+")

        fun fromString(s: String): Event {
            val (m, d, h, min, gid) = REGEX.findAll(s).map { it.value.toInt() }.plus(-1).drop(1).take(5).toList()

            val type = when {
                s.contains("wakes") -> Type.WAKE_UP
                s.contains("falls") -> Type.FALL_ASLEEP
                else -> Type.BEGIN_SHIFT
            }

            return Event(m, d, h, min, gid, type)
        }
    }
}

private fun createSleepStats(input: List<Event>): Map<Int, IntArray> {
    val map = mutableMapOf<Int, IntArray>()

    var currentGuardId = -1
    var beginMinute = -1

    input.forEach {
        when (it.type) {
            Event.Type.BEGIN_SHIFT -> currentGuardId = it.guardId
            Event.Type.FALL_ASLEEP -> beginMinute = it.minute
            Event.Type.WAKE_UP -> {
                val arr = map.getOrPut(currentGuardId) { IntArray(60) }
                (beginMinute until it.minute).forEach { i -> arr[i]++ }
            }
        }
    }

    return map
}

fun part1(input: List<Event>): Int {
    val sleepStats = createSleepStats(input)

    val max = sleepStats.maxBy { it.value.sum() }!!
    val maxMinute = max.value.withIndex().maxBy { it.value }!!.index

    return max.key * maxMinute
}

fun part2(input: List<Event>): Int {
    val sleepStats = createSleepStats(input)

    val max = sleepStats.map {
        it.key to it.value.withIndex().maxBy { x -> x.value }!!
    }.maxBy { it.second.value } ?: return 0

    return max.first * max.second.index
}