LeetCode 429. N叉树的层序遍历(N-ary Tree Level Order Traversal)

Posted 2021-11-29 hglibin

429. N叉树的层序遍历
429. N-ary Tree Level Order Traversal

LeetCode429. N-ary Tree Level Order Traversal

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)。

例如，给定一个 3 叉树:

返回其层序遍历:

[
     [1],
     [3,2,4],
     [5,6]
]

说明:

1. 树的深度不会超过 1000。
2. 树的节点总数不会超过 5000。
   

Java 实现

import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

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

    public Node() {
    }

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

class Solution {
    public List<List<Integer>> levelOrder(Node root) {
        List<List<Integer>> result = new LinkedList<>();
        Queue<Node> queue = new LinkedList<>();
        if (root == null) {
            return result;
        }
        queue.offer(root);
        while (!queue.isEmpty()) {
            List<Integer> list = new LinkedList<>();
            int size = queue.size();
            for (int i = 0; i < size; i++) {
                if (queue.peek().children != null) {
                    for (int j = 0; j < queue.peek().children.size(); j++) {
                        queue.offer(queue.peek().children.get(j));
                    }
                }
                list.add(queue.poll().val);
            }
            result.add(list);
        }
        return result;
    }
}

参考资料

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