aoc_2024/day11.kts

#!/usr/bin/env kotlin
import java.util.Scanner
import java.util.PriorityQueue


val scanner = Scanner(System.`in`)

class PriorityCache<K, V>(private val maxSize: Int) {
    private val cache = mutableMapOf<K, V>()
    private val priorityQueue = PriorityQueue<Pair<K, Int>>(compareBy { it.second }) // Pair(Key, Priority)

    fun put(key: K, value: V, priority: Int) {
        if (cache.size >= maxSize) {
            val leastPriority = priorityQueue.poll() // Remove the lowest-priority item
            cache.remove(leastPriority.first)
        }
        cache[key] = value
        priorityQueue.add(Pair(key, priority))
    }

    fun get(key: K): V? {
        return cache[key]
    }

    fun isCached(key: K): Boolean {
        return cache.containsKey(key)
    }
}
val priorityCache = PriorityCache<String, Long>(20000)
fun getStonesAfter(input: List<Long>,iterations: Int, cache: PriorityCache<String, Long>): Long {
    var sum = 0L
    for (i in input) {
        sum += getStoneNumber(i, iterations, cache)
        println("Done with $i")
    }
    return sum
}
fun getStoneNumber(number: Long, iterations: Int, cache: PriorityCache<String, Long>): Long {
    if (iterations == 0) {
        return 1L
    } else if (cache.isCached("$iterations-$number")) {
        return cache.get("$iterations-$number")!!
    } else if (number == 0L) {
        val stonesum =  getStoneNumber(1, iterations - 1, cache)
        cache.put("$iterations-0", stonesum, iterations)
        return stonesum
    } else if (number.toString().length % 2 == 0) {
        val mid = number.toString().length / 2
        val left = number.toString().substring(0, mid).toLong()
        val right = number.toString().substring(mid).toLong()
        val stonesum = getStoneNumber(left, iterations - 1, cache) + getStoneNumber(right, iterations - 1, cache)
        cache.put("$iterations-$number", stonesum, iterations)
        return stonesum
    } else {
        val newVal = number * 2024
        val stonesum = getStoneNumber(newVal, iterations - 1, cache)
        cache.put("$iterations-$number", stonesum, iterations)
        return stonesum
    }
}
val input = scanner.nextLine().split(" ").map { it.toLong() }
println("First part with 25 iterations: ${getStonesAfter(input, 25, priorityCache)}")
println("Second part with 75 iterations: ${getStonesAfter(input, 75, priorityCache)}")