This C++ Program Checks if a Binary Tree is a Binary Search Tree.

Here is source code of the C++ Program to check if a Binary Tree is a BST. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

`/*`

`* C++ Program to Check if a Binary Tree is a BST`

`*/`

`#include <iostream>`

`#include <cstdlib>`

`#include <climits>`

using namespace std;

`/*`

`* Node Declaration`

`*/`

`struct node`

`{`

int data;

node* left;

node* right;

};

int isBSTUtil(node* node, int min, int max);

`/*`

`* Returns true if the given tree is a binary search tree`

`*/`

int isBST(node* node)

`{`

return(isBSTUtil(node, INT_MIN, INT_MAX));

`}`

`/*`

`* Returns true if the given tree is a BST and its`

`* values are >= min and <= max.`

`*/`

int isBSTUtil(struct node* node, int min, int max)

`{`

if (node==NULL)

return 1;

if (node->data < min || node->data > max)

return 0;

return isBSTUtil(node->left, min, node->data - 1) &&

isBSTUtil(node->right, node->data + 1, max);

`}`

`/*`

`* allocates a new node with the data and NULL left and right pointers.`

`*/`

node* newNode(int data)

`{`

node* nod = new node;

nod->data = data;

nod->left = NULL;

nod->right = NULL;

return nod;

`}`

`/*`

`* Main`

`*/`

int main()

`{`

node *root = newNode(4);

root->left = newNode(2);

root->right = newNode(5);

root->left->left = newNode(1);

root->left->right = newNode(3);

if (isBST(root))

cout<<"The Given Binary Tree is a BST"<<endl;

`else`

cout<<"The Given Binary Tree is not a BST"<<endl;

return 0;

`}`

$ g++ binary_bst.cpp $ a.out The Given Binary Tree is a BST ------------------ (program exited with code: 1) Press return to continue

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