Advent of code 2022/18

Ajax Direct

foreach ($input->lines as $line) {
    $sphere[] = explode(",", $line);
}

function get_sides($cube)
{
    [$x, $y, $z] = $cube;
    return [
        [$x - 1, $y, $z],
        [$x + 1, $y, $z],
        [$x, $y + 1, $z],
        [$x, $y - 1, $z],
        [$x, $y, $z + 1],
        [$x, $y, $z - 1]
    ];
}

function dfs($start, $sphere)
{
    $todo = [$start];
    $done = [];

    while ($todo && count($done) < 15000) {
        $current = array_shift($todo);
        $done[] = $current;

        foreach (get_sides($current) as $side) {
            if ($current[0] < -1 || $current[1] < -1 || $current[2] < -1) continue;
            if ($current[0] > 20 || $current[1] > 20|| $current[2] > 20) continue;
            if (!in_array($side, $done) && !in_array($side, $todo) && !in_array($side, $sphere)) {
                $todo[] = $side;
            }
        }
    }

    return $done;
}

function get_solution($sphere, $outside = [])
{
    $sides = 0;

    foreach ($sphere as $cube) {
        $sides += 6;
        foreach (get_sides($cube) as $side) {

            if ($outside && !in_array($side, $outside)) {
                $sides--;
            } elseif (in_array($side, $sphere)) {
                $sides--;
            }
        }
    }
    return $sides;
}


// ==================================================
// > SOLUTIONS
// ==================================================
$solution_1 = get_solution($sphere);
$solution_2 = get_solution($sphere, dfs([0, 0, 0], $sphere));