Advent of Code v Kotlinu (Den 2.)

Doháním deficit a zde je řešení pro den 2.

A:

fun hasSameLettersCount(id: String, occurrences: Int): Boolean {
    val sameLetterCounts = id.groupBy { it }
        .values
        .map { it.count() }

    return occurrences in sameLetterCounts
}

fun main() {
    val ids = File("input2.txt").readLines()

    val twoCounts = ids.filter { hasSameLettersCount(it, 2) }.count()
    val threeCounts = ids.filter { hasSameLettersCount(it, 3) }.count()

    println(twoCounts * threeCounts)
}

B:

fun main() {
    val ids = File("input2.txt").readLines().toSet()

    for (idA in ids) {
        for (idB in ids) {
            val diff = getDiff(idA, idB)
            if (diff.length == idA.length - 1) {
                println(diff)
                return
            }
        }
    }
}

fun getDiff(first: String, second: String) = first.zip(second) { a, b ->
    if (a == b) a.toString() else ""
}.joinToString("")