aoc2022d21.kt

import se.saidaspen.aoc.util.Day
import se.saidaspen.aoc.util.words
import kotlin.math.absoluteValue
import kotlin.math.max

fun main() = Dayxx.run()

object Dayxx : Day(2022, 21) {

    var input2 = "root: pppw + sjmn\n" +
            "dbpl: 5\n" +
            "cczh: sllz + lgvd\n" +
            "zczc: 2\n" +
            "ptdq: humn - dvpt\n" +
            "dvpt: 3\n" +
            "lfqf: 4\n" +
            "humn: 5\n" +
            "ljgn: 2\n" +
            "sjmn: drzm * dbpl\n" +
            "sllz: 4\n" +
            "pppw: cczh / lfqf\n" +
            "lgvd: ljgn * ptdq\n" +
            "drzm: hmdt - zczc\n" +
            "hmdt: 32"
    override fun part1(): Any {
        val monkeys = input.lines().map { it.split(":").map { t -> t.trim() } }.associate { it[0] to it[1] }
        return getValue(monkeys, "root")
    }

    private fun getValue(monkeys: Map<String, String>, m: String): Long {
        val monkeyDo = monkeys[m]!!
        return if (monkeyDo.toLongOrNull() != null) {
            monkeyDo.toLong()
        } else {
            val (op1, oper, op2) = words(monkeyDo)
            when (oper) {
                "+" -> getValue(monkeys, op1) + getValue(monkeys, op2)
                "-" -> getValue(monkeys, op1) - getValue(monkeys, op2)
                "*" -> getValue(monkeys, op1) * getValue(monkeys, op2)
                "/" -> getValue(monkeys, op1) / getValue(monkeys, op2)
                else -> throw RuntimeException("Unsupported op")
            }
        }
    }

    override fun part2(): Any {
        val monkeys: MutableMap<String, String> =
            input.lines().map { it.split(":").map { t -> t.trim() } }.associate { it[0] to it[1] }.toMutableMap()
        var currentGuess = 0L
        var switch = false
        var lastDiff = 0L
        while (true) {
            val dist = guess(monkeys, currentGuess)
            if (dist.absoluteValue > lastDiff.absoluteValue && currentGuess != 0L) switch = !switch // Change direction if we are going in the wrong dir
            if (dist == 0L) return currentGuess
            println("guessed $currentGuess gave $dist")
            var change = max(1, dist.absoluteValue / 2)
            change *= if (switch) -1 else 1
            currentGuess += if (dist > 0) change else change * -1
            lastDiff = dist
        }
    }

    private fun guess(
        monkeys: MutableMap<String, String>,
        currentGuess: Long,
    ): Long {
        val (op1, _, op2) = words(monkeys["root"]!!)
        monkeys["humn"] = currentGuess.toString()
        return getValue(monkeys, op1) - getValue(monkeys, op2)
    }
}