AOC day 15 Kotlin

day_15.kt

fun main(){
    val time = measureTimeMillis {  println(findNumber(at = 29999999)) }
    println(time/1000)
}


fun findNumber(at : Int) : Int {
    val my_puzzle = mutableListOf<Int>(0,12,6,13,20,1,17)
    var lastRegistered = mutableMapOf<Int, Int>()
    for (x in 0..my_puzzle.lastIndex) lastRegistered[my_puzzle[x]] = x

    for (x in (my_puzzle.size - 1)..at) {
        if (lastRegistered[my_puzzle[x]] == null){
            lastRegistered[my_puzzle[x]] = my_puzzle.lastIndex
            my_puzzle.add(0)

        } else {
            my_puzzle.add(my_puzzle.lastIndex - lastRegistered[my_puzzle[x]]!!)
            lastRegistered[my_puzzle[x]] = my_puzzle.lastIndex - 1
        }


    }

    return (my_puzzle[at])
}