isBST?

/* Hidden stub code will pass a root argument to the function below. Complete the function to solve the challenge. Hint: you may want to write one or more helper functions.

The Node struct is defined as follows:
   struct Node {
      int data;
      Node* left;
      Node* right;
   }
*/


bool left(Node *root , int n){
    if(root == NULL){
        return 1;
    }else if(root->data >= n){
        return 0;
    }else{
        return left(root->left , root->data)
            && left(root->left , n)
            && left(root->right , n)
            && right(root->right, root->data);
    }
}

bool right (Node *root , int n){
    if(root == NULL){
        return 1;
    }else if(root->data <= n){
        return 0;
    }else{
        return right(root->right , root->data)
            && right(root->right, n)
            && right(root->left , n)
            && left(root->left , root->data);
    }
}

bool checkBST(Node * root) {
   if(root == NULL) return true;
    return right(root->right , root->data) && left(root->left , root->data);

}