Advent of code 2017/12

Ajax Direct

$nodes = $input->lines->mapAssoc(fn ($i, $line) =>
    [$line->numbers()[0] => array_fill_keys((array) $line->numbers()->slice(1), 1)]
);

function get_group($nodes, $start) {
    $queue   = [$start];
    $visited = [];

    while (!empty($queue)) {
        $current = array_shift($queue);
        $visited[] = $current;

        foreach ($nodes[$current] as $state => $relation) {
            if (!in_array($state, $queue) && !in_array($state, $visited)) {
                $queue[] = $state;
            }
        }
    }

    return $visited;
}

// ==================================================
// > PART 1
// ==================================================
$solution_1 = count(get_group($nodes, 0));

// ==================================================
// > PART 2
// ==================================================
$solution_2 = 0;
while (!$nodes->empty()) {
    $solution_2++;
    $group = get_group($nodes, $nodes->keys()[0]);
    $nodes = $nodes->removeKeys($group);
}