# Count all pairs of adjacent nodes whose XOR is an odd number in C++

In this tutorial, we will be discussing a program to find the number of pairs of adjacent nodes whose XOR is an odd number.

For this we will be provided with a binary tree. Our task is to count the number of pairs of adjacent elements whose XOR is an odd number.

## Example

Live Demo

#include <iostream>
using namespace std;
//node structure of tree
struct Node {
int data;
struct Node *left, *right;
};
//finding the pairs whose XOR
//is odd
int count_pair(Node* root, Node *parent=NULL){
if (root == NULL)
return 0;
//checking pair of XOR is odd or not
int res = 0;
if (parent != NULL && (parent->data ^ root->data) % 2)
res++;
return res + count_pair(root->left, root) + count_pair(root->right, root);
}
//creation of new node
Node* newNode(int data){
Node* temp = new Node;
temp->data = data;
temp->left = NULL;
temp->right = NULL;
return temp;
}
int main(){
struct Node* root = NULL;
root = newNode(15);
root->left = newNode(13);
root->left->left = newNode(12);
root->left->right = newNode(14);
root->right = newNode(18);
root->right->left = newNode(17);
root->right->right = newNode(21);
printf("%d ", count_pair(root));
return 0;
}

## Output

5

Updated on: 10-Feb-2020

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