public List<List<Integer>> traverse(TreeNode root) {
    List<List<Integer>> result = new ArrayList<>();

    LinkedList<TreeNode> ll = new LinkedList<>();

    ll.add(root);

    int listSize = 0;
    List<Integer> numbers = new ArrayList<>();

    int kids = 0;
    int level = 1;
    while (!ll.isEmpty()) {
        if (listSize == level) {
            result.add(numbers);
            level = level * kids;
            listSize = 0;
            numbers = new ArrayList<>();
            kids = 0;
            continue;
        }


        TreeNode popped = ll.poll();

        numbers.add(popped.val);
        listSize++;

        if (popped.left != null) {
            ll.add(popped.left);
            kids++;
        }

        if (popped.right != null) {
            ll.add(popped.right);
            kids++;
        }
    }

    result.add(numbers);
    return result;
}