Advent of code 2020/14

Ajax Direct

$mem_1 = $mem_2 = [];
foreach ($input->lines as $line) {
    [$a, $b] = $line->split(" = ");

    if ($a == "mask") {
        $mask_0 = bindec($b->replace("X", 1));
        $mask_1 = bindec($b->replace("X", 0));
        $mask_x = bindec($b->replace("0", "1")->replace("X", "0"));
        $pos_x  = $b->chars->keep("X")->keys();
        continue;
    }

    // Part 1
    $pos = int($a->sub(4, -1));
    $mem_1[$pos] = (int($b) & $mask_0) | $mask_1;

    // Part 2
    $pos = ($pos | $mask_1) & $mask_x;
    $mem_2[$pos] = int($b);
    foreach ($pos_x->combinations() as $cx) {
        $m = 0;
        foreach ($cx as $x) $m += 2 ** (35 - $x);
        $mem_2[$pos | $m] = int($b);
    }
}

$solution_1 = array_sum($mem_1);
$solution_2 = array_sum($mem_2);