题目:
题解:
class Solution {public List<List<Integer>> levelOrder(Node root) {if (root == null) {return new ArrayList<List<Integer>>();}List<List<Integer>> ans = new ArrayList<List<Integer>>();Queue<Node> queue = new ArrayDeque<Node>();queue.offer(root);while (!queue.isEmpty()) {int cnt = queue.size();List<Integer> level = new ArrayList<Integer>();for (int i = 0; i < cnt; ++i) {Node cur = queue.poll();level.add(cur.val);for (Node child : cur.children) {queue.offer(child);}}ans.add(level);}return ans;}
}