import java.io.File
import kotlin.text.Regex

fun main() {
    val input = File("input")

    val races = parseRaces(input)
    println(part1(races))

    val singleRace = parseSingleRace(input)
    println(part1(listOf(singleRace)))
}

fun part1(races: List<Pair<Long, Long>>): Long {
    return races.map { getNumberOfWins(it.first, it.second) }.reduce { count, acc -> count * acc }
}

fun getNumberOfWins(time: Long, distance: Long): Long {
    val wins = (0..time / 2).filter { it * (time - it) > distance }.count()

    return when (time % 2) {
        0L -> (wins - 1L) * 2L + 1L
        1L -> wins * 2L
        else -> throw Exception("Unreachable")
    }
}

fun parseSingleRace(input: File): Pair<Long, Long> {
    return input.useLines {
        val numbers =
                it
                        .map { it.split(':').drop(1).single().filter { it.isDigit() }.toLong() }
                        .iterator()
        Pair(numbers.next(), numbers.next())
    }
}

fun parseRaces(input: File): List<Pair<Long, Long>> {
    return input.useLines {
        val numbers = it.map { it.split(Regex("\\s+")).drop(1).map { it.toLong() } }.iterator()
        numbers.next().zip(numbers.next()).map { (time, distance) -> Pair(time, distance) }
    }
}