Advent of code 2024/7

Ajax Direct

function solve($input, $ops) {
    return $input->lines->map(function ($l) use ($ops) {
        $n = (array) $l->numbers();
        $goal = array_shift($n);
        $queue = [$n];

        while ($n = array_pop($queue)) {
            $digit = array_shift($n);

            foreach ($ops as $op) {
                $try = $n;
                $try[0] = $op($digit, $try[0]);

                if (count($try) == 1) {
                    if ($try[0] == $goal) return $goal;
                } else {
                    // Stop if lowest possible is over
                    if (array_sum(array_diff($try, [1])) > $goal) continue;
                    // Stop if highest possible is bellow
                    if (implode("", $try) < $goal) continue;

                    $queue[] = $try;
                }
            }
        }

        return 0;
    })->sum();
}

// ==================================================
// > PART 1
// ==================================================
$op = [
    "+" => fn ($a, $b) => $a + $b,
    "*" => fn ($a, $b) => $a * $b,
];
$solution_1 = solve($input, $op);

// ==================================================
// > PART 2
// ==================================================
$op["||"] = fn ($a, $b) => $a . $b;

$solution_2 = solve($input, $op);