100 Prisoners Riddle

100-prisoners-riddle.kt

fun main() {
    var allUnder = 0
    var anyOver = 0

    repeat(500_000) {
        val boxes = (0 until 100).toList().shuffled()

        if (allUnderFifty(boxes)) {
            allUnder++
        } else {
            anyOver++
        }
    }

    println(allUnder.toDouble() / (anyOver + allUnder).toDouble())
}

fun allUnderFifty(boxes: List<Int>): Boolean {
    (0 until 100).forEach {
        if (findYourNumber(boxes, it) > 50) {
            return false
        }
    }

    return true
}

fun findYourNumber(boxes: List<Int>, number: Int): Int {
    var counter = 0
    var n = number

    while (true) {
        counter++
        n = boxes[n]

        if (n == number) {
            return counter
        }
    }
}