429. N-ary Tree Level Order Traversal | Leetcode solution

 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, 104]

solution:

/*

// Definition for a Node.

class Node {

public:

    int val;

    vector<Node*> children;

    Node() {}

    Node(int _val) {

        val = _val;

    }

    Node(int _val, vector<Node*> _children) {

        val = _val;

        children = _children;

    }

};

*/

class Solution {

public:

    vector<vector<int>> levelOrder(Node* root) {

        

        vector<vector<int>>result;

        queue<Node*>q1;

        queue<Node*>q2;

        q1.push(root);

        if(root == NULL)

        {   

            return result;

        }

        result.push_back({q1.front()->val});

        int i = 0;

        while(true)

        {

            vector<int>j;

        while(!q1.empty())

        {

            Node *temp = q1.front();

            vector<Node*>vect = temp->children;

            int s = vect.size();

            for(int l =0 ; l < s ; l++)

            {

                if(vect[l] != NULL)

                {

                    q2.push(vect[l]);

                    j.push_back(vect[l]->val);

                }

            }

            

            q1.pop();

            

        }   

            result.push_back(j);

            if(q2.empty())

                break;

            q1 = q2;

            while(!q2.empty())

            {

                  q2.pop();

            }

            i++;

        }

        result.pop_back();

        

      return result;

    }

};

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