# Binary Tree Level Order Traversal

Given the `root` of a binary tree, return the level order traversal of its nodes’ values. (i.e., from left to right, level by level).

Example 1:

```Input: root = [3,9,20,null,null,15,7]
Output: [[3],[9,20],[15,7]]
```

Example 2:

```Input: root = [1]
Output: [[1]]
```

Example 3:

``````/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode() : val(0), left(nullptr), right(nullptr) {}
*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
vector<vector<int>> levelOrder(TreeNode* root) {
vector<vector<int>> ans;
queue<TreeNode*> q;

if(root)
q.push(root);

int i = 0;

while(!q.empty()){

vector<int> temp;
int n = q.size();

for(int i=0;i<n;i++){

TreeNode* _node = q.front();
q.pop();

temp.push_back(_node->val);

if(_node->left)
q.push(_node->left);

if(_node->right)
q.push(_node->right);
}
ans.push_back(temp);
}

return ans;
}
};``````