int prev_ele=INT_MIN; 

bool inorder_traversal(Node* root){
    if(root==NULL)return true;
    if(inorder_traversal(root->left)==false)return false;
    if(prev_ele>=root->data)return false;
    prev_ele=root->data;
    return inorder_traversal(root->right);
}

bool isBST(Node* root){
    prev_ele=INT_MIN;
    return inorder_traversal(root);
}

//Time  Complexity:O(nodes)
//Space Complexity:O(height)