fun main() {
    fun getPriority(c: Char): Int {
        return if (c.isLowerCase()) c.code - 'a'.code + 1
        else c.code - 'A'.code + 27
    }

    fun part1(input: List<String>) = input.sumOf { it ->
        it.subSequence(0 until it.length / 2)
            .toSet()
            .intersect(it.subSequence(it.length / 2, it.length).toSet())
            .map { getPriority(it) }
            .single()
    }

    fun part2(input: List<String>) = input.chunked(3).sumOf { it ->
        it[0].toSet()
            .intersect(it[1].toSet())
            .intersect(it[2].toSet())
            .map { getPriority(it) }
            .single()
    }

    // test if implementation meets criteria from the description, like:
    val testInput = readInput("Day03_test")
    check(part1(testInput) == 157)
    check(part2(testInput) == 70)

    val input = readInput("Day03")
    println(part1(input))
    println(part2(input))
}
