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  1.  #include <iostream>
  2. using namespace std;
  3.  
  4. struct Node {
  5.     int key;
  6.     Node *left, *right;
  7.     Node(int val) {
  8.         key = val;
  9.         left = NULL;
  10.         right = NULL;
  11.     }
  12. };
  13.  
  14. // Check for BST
  15. bool isBST(Node *root, Node *min = NULL, Node *max = NULL) {
  16.     if (root == NULL)
  17.         return true;
  18.     if (min != NULL && root->key <= min->key) {
  19.         return false;
  20.     }
  21.     if (max != NULL && root->key >= max->key) {
  22.         return false;
  23.     }
  24.     bool leftValid = isBST(root->left, min, root);
  25.     bool rightValid = isBST(root->right, root, max);
  26.     return leftValid && rightValid;
  27. }
  28.  
  29. int main() {
  30.     Node *root1 = new Node(2); // Fixing root key to 2
  31.     root1->left = new Node(1); // Inserting 1 as left child
  32.     root1->right = new Node(3); // Inserting 3 as right child
  33.  
  34.     if (isBST(root1, NULL, NULL))
  35.         cout << "Valid BST" << endl;
  36.     else
  37.         cout << "Invalid BST" << endl;
  38.  
  39.     return 0;
  40. }
  41.  
Success #stdin #stdout 0s 5296KB
comments (?)
stdin 
Standard input is empty
stdout 
Valid BST
https://ideone.com/Uhh3Kd
language:
C++ (gcc 8.3)
created:
14 days ago
visibility:
public

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