Advent of code 2022/21

Ajax Direct

$monkeys = [];

// Parse
foreach ($input->lines as $line) {
    preg_match("/^([a-z]+)\: (.+)$/", $line, $matches);
    if (is_numeric($matches[2]) ) {
        $monkeys[$matches[1]] = (int) $matches[2];
    } else {
        $monkeys[$matches[1]] = explode(" ", $matches[2]);
    }
}

function get_solution($monkeys)
{
    $previous_missing_monkeys = $missing_monkeys = [];

    // Do operations
    while (!is_int($monkeys["root"])) {
        foreach ($monkeys as $monkey => $value) {
            if (is_array($value) && is_int($monkeys[$value[0]]) && is_int($monkeys[$value[2]])) {
                switch ($value[1]) {
                    case "+": $monkeys[$monkey] = $monkeys[$value[0]] + $monkeys[$value[2]]; continue 2;
                    case "-": $monkeys[$monkey] = $monkeys[$value[0]] - $monkeys[$value[2]]; continue 2;
                    case "/": $monkeys[$monkey] = $monkeys[$value[0]] / $monkeys[$value[2]]; continue 2;
                    case "*": $monkeys[$monkey] = $monkeys[$value[0]] * $monkeys[$value[2]]; continue 2;
                    case "=": return $monkeys[$value[0]] - $monkeys[$value[2]];
                }
            }

            if (is_array($value)) {
                $missing_monkeys[] = $monkey;
            }
        }

        // Abort if no new monkey was discoverd and we are stuck in a loop
        if ($missing_monkeys == $previous_missing_monkeys) {
            return false;
        }
        $previous_missing_monkeys = $missing_monkeys;
        $missing_monkeys = [];
    }

    return $monkeys["root"];
}

// =============================================================================
// > PART 1
// =============================================================================
$solution_1 = get_solution($monkeys);

// ==================================================
// > PART 2
// > Solution was found by semi-bruteforce.
// > Testing all numbers from 0 to 300 000 revealed that
// > each 10 935 increase starting from 1200, we got 426 560 closer to the solution.
// > Extrapolating this, I was able to find the number of increases needed to reach it.
// ==================================================
$monkeys["root"][1] = "=";

$solution_2 = false;
$found = [];

for ($n = 0; $n <= 0; $n++) { // Was used to get the progression from 0 to 300000
    $test = $monkeys;
    $test["humn"] = $n;

    if (($diff = get_solution($test)) === 0) {
        $solution_2 = $n;
        break;
    } elseif ($diff) {
        $found[$n] = $diff;
    }
}

$solution_2 = 1200 + (282869317 * 10935);