```
bool isValidBST(TreeNode *root){
if (root == NULL || (root->left == NULL && root->right == NULL))
return 1;
if (root->left != NULL){
if (root->left->val >= root->val)
return 0;
else
return 1 && isValidBST(root->left);
}
if (root->right != NULL){
if (root->right->val <= root->val)
return 0;
else
return 1 && isValidBST(root->right);
}
}
```

Submission Result: **Wrong Answer**

Input: {10,5,15,#,#,6,20}

Output: true

Expected: false