3. 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]]

Solution: (BFS)

/*
// 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>> res;
        
        if(root == NULL){
            return res;
        }
        queue<Node *> q;
        
        q.push(root);
       
        
        
        while (!q.empty())
        {
            int s = q.size();
            vector<int> v;
            
            while (s--)
            {

                Node *t = q.front();
                q.pop();
                v.push_back(t->val);
                
                for (int i = 0; i < t->children.size(); i++)
                {
                    if (t->children[i])
                    {
                        q.push(t->children[i]);
                    }
                }
            }

            res.push_back(v);
        }
        
        return res;
    }
};