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leetCode-429:N-ary Tree Level Order Traversal

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问题描述

给定一个 n 叉树，要求输出其每一层的节点。题目链接：点我

样例输入输出

输入：root = [1,null,3,2,4,null,5,6]

输出：[[1],[3,2,4],[5,6]]

解释：树的形状如下

输入：root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]

输出：[[1],[2,3,4,5],[6,7,8,9,10],[11,12,13],[14]]

解释：树的形状如下

问题解法

此题简单，就是单纯的广度优先搜索，代码如下

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/*
// Definition for a Node.
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>> result = new LinkedList<>();
        if (root == null) {
            return result;
        }
        
        Queue<Node> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            List<Integer> nums = new LinkedList<>();
            for (int i = queue.size(); i > 0; i--) {
                Node node = queue.poll();
                nums.add(node.val);
                queue.addAll(node.children);
            }
            result.add(nums);
        }
        
        return result;
    }
}