【LeeCode】429.N叉树的层序遍历

【题目描述】

给定一个 N 叉树，返回其节点值的层序遍历。（即从左到右，逐层遍历）。

树的序列化输入是用层序遍历，每组子节点都由 null 值分隔（参见示例）。

​​https://leetcode.cn/problems/n-ary-tree-level-order-traversal/​​

【示例】

【代码】​​代码随想录​​

package com.company;

import java.util.*;

class Node {
    public int val;
    public List<Node> children;

    public Node() {}

    public Node(int _val) {
        val = _val;
    }

    public Node(int _val, List<Node> _children) {
        val = _val;
        children = _children;
    }
};


class Solution {
    public List<List<Integer>> levelOrder(Node root) {
        List<List<Integer>> res = new LinkedList<>();
        Deque<Node> deque = new LinkedList<>();
        if (root == null) return res;
        deque.offerLast(root);
        while (!deque.isEmpty()){
            int len = deque.size();
            List<Integer> list = new LinkedList<>();
            Node node = deque.pollFirst();
            list.add(node.val);
            List<Node> children = node.children;
            if (children == null || children.size() == 0) continue;
            for (Node child : children) {
                if (child != null){
                    deque.offerLast(child);
                }
            }
            res.add(list);
        }
        return res;
    }
}
public class Test {
    public static void main(String[] args) {

    }
}