429. N-ary Tree Level Order Traversal - LeetCode

Question

429. N-ary Tree Level Order Traversal

Solution

题目大意：

N叉树，返回每层的值，从上到下，从左到右

思路：

利用队列遍历这个N叉树

Java实现：

public List<List<Integer>> levelOrder(Node root) {
    // N叉树的遍历
    List<List<Integer>> retList = new ArrayList<>();
    if (root == null) return retList;
    Queue<Node> nodeQueue = new LinkedList<>();
    nodeQueue.offer(root);
    while(!nodeQueue.isEmpty()) {
        List<Integer> layerNodeList = new ArrayList<>();
        int curLayerSize = nodeQueue.size();
        for (int i = 0; i < curLayerSize; i++) {
            Node cur = nodeQueue.poll();
            layerNodeList.add(cur.val);
            if (cur.children != null) {
                for (Node tmp : cur.children) {
                    nodeQueue.offer(tmp);
                }
            }
        }
        retList.add(layerNodeList);
    }
    return retList;
}