C++ Program to Check if a Tree is Binary Search Tree

This C++ program checks whether the nodes entered form a binary search tree, a tree consisting of only two child nodes.

Here is the source code of the C++ program to display whether the nodes given as input give a binary search tree as output or not. This C++ program is successfully compiled and run on DevCpp, a C++ compiler. The program output is given below.

```
/*
```

 * C++ Program To Check Whether a Given Tree is Binary Search Tree

```
 */
```
```
#include<stdio.h>
```
```
#include<stdlib.h>
```
```
#include<limits.h>
```
```
#include<iostream>
```
```
using namespace std;
```
```
struct node
```
```
{
```
```
    int data;
```
```
    struct node* left;
```
```
    struct node* right;
```
```
}*node1 = NULL;
```

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);

```
} 
```
```
int isBST(struct node* node) 
```
```
{ 
```

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

```
} 
```
```
struct node* newNode(int data)
```
```
{
```
```
    node1 = new node;
```
```
    node1->data = data;
```
```
    node1->left = NULL;
```
```
    node1->right = NULL;
```
```
    return(node);
```
```
}
```
```
int main()
```
```
{
```
```
    struct 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<<"Is BST";
```
```
    else
```
```
        cout<<"Not a BST";   
```
```
    getch();
```
```
}
```

Output
Is BST

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