class Day3 {

    fun solvePart1(input: String) =
        getOverlappingCells(parse(input))
            .count()
            .toString()

    fun solvePart2(input: String): String {
        val claims = parse(input)
        val disqualified = getOverlappingCells(claims)
        return claims.first { claim -> claim.cells.none { it in disqualified } }.id.toString()
    }

    private fun parse(input: String) = input.lines().map(Claim.Companion::parse)

    private fun getOverlappingCells(claims: List<Claim>): Set<Pair<Int, Int>> =
        claims
            .flatMap { it.cells }
            .groupingBy { it }
            .eachCount()
            .filterValues { it > 1 }
            .keys

}

private data class Claim(
    val id: Int,
    val left: Int,
    val top: Int,
    val width: Int,
    val height: Int
) {
    val cells = (left until left + width).flatMap { x -> (top until top + height).map { y -> Pair(x, y) } }

    companion object {
        val pattern = Regex("""#(\d+) @ (\d+),(\d+): (\d+)x(\d+)""")
        fun parse(line: String): Claim {
            return (pattern
                .matchEntire(line) ?: throw IllegalArgumentException("Invalid input: $line"))
                .groupValues
                .drop(1)
                .map(String::toInt)
                .let { groups -> Claim(groups[0], groups[1], groups[2], groups[3], groups[4]) }
        }
    }
}