val input = readText("y2019/w1/d02/input.txt")

fun main() {
    val program = input.split(",").map(String::toInt).toMutableList()

    println("Part 1: " + run(program, 12, 2))

    for (noun in 0 until 100)
        for (verb in 0 until 100)
            if (run(program, noun, verb) == 19690720)
                println("Part 2: " + (100 * noun + verb))
}

private fun run(program: List<Int>, noun: Int, verb: Int): Int {
    val memory = program.toMutableList()
    memory[1] = noun
    memory[2] = verb

    var instrPtr = 0;

    loop@while (true) {
        val op: (Int, Int) -> Int = when(val opcode = memory[instrPtr]) {
            1 -> Int::plus
            2 -> Int::times
            99 -> break@loop
            else -> error("unknown opcode $opcode")
        }

        memory[memory[instrPtr + 3]] = op(memory[memory[instrPtr + 1]], memory[memory[instrPtr + 2]])
        instrPtr += 4
    }

    return memory[0]
}