1.     public List<List<Integer>> levelOrder(Node root) {
    2.         List<List<Integer>> list = new LinkedList<>();
    3.         Deque<Node> deque = new LinkedList();
    4.         if (root != null) {
    5.             deque.addLast(root);
    6.         }
    7.         while (!deque.isEmpty()) {
    8.             LinkedList<Integer> tempList = new LinkedList<>();
    9.             // 队列长度
    10.             int size = deque.size();
    11.             while (size-- > 0) {
    12.                 Node poll = deque.pollFirst();
    13.                 for (Node child : poll.children) {
    14.                     deque.addLast(child);
    15.                 }
    16.                 tempList.add(poll.val);
    17.             }
    18.             list.add(tempList);
    19.         }
    20.         return list;
    21.     }
    1.     public List<List<Integer>> levelOrder(Node root) {
    2.         List<List<Integer>> ans = new ArrayList<>();
    3.         dfs(root, ans, 0);
    4.         return ans;
    5.     }
    6.     void dfs(Node node, List<List<Integer>> ans, int level) {
    7.         if (node == null) return;
    8.         if (ans.size() == level) ans.add(new ArrayList<>());
    9.         ans.get(level).add(node.val);
    10.         for (Node child : node.children) dfs(child, ans, level + 1);
    11.     }