429. N-ary Tree Level Order Traversal

Given an n-ary tree, return the level order traversal of its nodes' values.

Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples).

Example 1:

Input: root = [1,null,3,2,4,null,5,6]
Output: [[1],[3,2,4],[5,6]]

Example 2:

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

Constraints:

• The height of the n-ary tree is less than or equal to 1000
• The total number of nodes is between [0, 10^4]

class Solution {
public:
    vector<vector<int>> levelOrder(Node* root) {
     vector<vector<int>> res;
        vector<Node*> node,tmp;
        if(root)node.push_back(root);
        while(!node.empty())
        {
            vector<int> row;
            for(Node *p:node)
            {
                row.push_back(p->val);
                for(Node *c:p->children)
                {
                    if(c)
                        tmp.push_back(c);
                }
            }
            res.push_back(row);
            node=tmp;
            tmp.clear();
        }
        return res;
    }
};