LeetCode #429. N-ary Tree Level Order Traversal

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本文介绍了一种解决N叉树层次遍历问题的方法，通过使用队列实现从上到下，从左到右的层次遍历，返回每一层节点的值。此算法适用于深度最多为1000的树，总节点数不超过5000。

题目描述：

Given an n-ary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).

For example, given a 3-ary tree:

We should return its level order traversal:

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

Note:

The depth of the tree is at most 1000.
The total number of nodes is at most 5000.

class Solution {
public:
    vector<vector<int>> levelOrder(Node* root) {
        vector<vector<int>> result;
        if(root==NULL) return result;
        queue<Node*> q;
        q.push(root);
        while(!q.empty())
        {
            int n=q.size();
            vector<int> cur;
            for(int i=0;i<n;i++)
            {
                Node* node=q.front();
                q.pop();
                cur.push_back(node->val);
                for(Node* child:node->children)
                    q.push(child);
            }
            result.push_back(cur);
        }
        return result;
    }
};