# leet Code : Validate Binary Search Tree Java || C++ || C || pYthon

Given the `root` of a binary tree, determine if it is a valid binary search tree (BST).

valid BST is defined as follows:

• The left subtree of a node contains only nodes with keys less than the node’s key.
• The right subtree of a node contains only nodes with keys greater than the node’s key.
• Both the left and right subtrees must also be binary search trees.

Example 1:

```Input: root = [2,1,3]
Output: true```

Solution

``````/**
* 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;
}
};``````