package aoc2024

import println
import readInput
import splitLongs

/*
--- Day 11: Plutonian Pebbles ---
https://adventofcode.com/2024/day/11
*/
fun main() {

    val inlineTestInput = """
        125 17
"""

    val powTenTable = generateSequence(1L) { it * 10L }.take(20).toList().toLongArray()
    val lookupTable = HashMap<Pair<Long, Int>, Long>()

    fun fastCeilLog10(n: Long): Int {
        for (i in 1 until powTenTable.size) {
            if (powTenTable[i] > n) return i
        }
        return -1
    }

    fun rec(n: Long, i: Int): Long {
        //println("$i $n")
        if (i == 0) return 1
        val ll = lookupTable[n to i]
        if (ll != null) return ll
        val result = if (n == 0L) {
            rec(1L, i - 1)
        } else {
            val size = fastCeilLog10(n)
            if (size and 1 == 0) {
                val left = n / powTenTable[size / 2]
                val right = n % powTenTable[size / 2]
                rec(left, i - 1) + rec(right, i - 1)
            } else {
                rec(n * 2024L, i - 1)
            }
        }
        lookupTable[n to i] = result
        return result
    }

    fun part1(input: List<String>): Long {
        val numbers = input[0].splitLongs()
        return numbers.sumOf { rec(it, 25) }
    }

    fun part2(input: List<String>): Long {
        val numbers = input[0].splitLongs()
        return numbers.sumOf { rec(it, 75) }
    }

    // test if implementation meets criteria from the description, like:
    val testInput = inlineTestInput.trim().reader().readLines()
    //val testInput = readInput("aoc2024/Day11_test")
    val testInputPart1Result = part1(testInput)
    println("Part 1 Test: $testInputPart1Result")
    val testInputPart2Result = part2(testInput)
    println("Part 2 Test: $testInputPart2Result")
    check(testInputPart1Result == 55312L)
    //check(testInputPart2Result == 0L)

    val input = readInput("aoc2024/Day11")
    part1(input).println()
    part2(input).println()
}