# Number of pairs whose sum is a power of 2 in C++

C++Server Side ProgrammingProgramming

In this tutorial, we are going to write a program that counts the number of pairs whose sum is a power of 2.

Let's see the steps to solve the problem.

• Write two loops to get all the pairs of the array.

• Compute the sum of every pair.

• Check whether the sum is a power of 2 or not using bitwise AND.

• Increment the count if the count is a power of 2.

## Example

Let's see the code.

Live Demo

#include <bits/stdc++.h>
using namespace std;
int get2PowersCount(int arr[], int n) {
int count = 0;
for (int i = 0; i < n; i++) {
for (int j = i + 1; j < n; j++) {
int sum = arr[i] + arr[j];
if ((sum & (sum - 1)) == 0) {
count++;
}
}
}
return count;
}
int main() {
int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int n = 10;
cout << get2PowersCount(arr, n) << endl;
return 0;
}

## Output

If you run the above code, then you will get the following result.

6

## Conclusion

If you have any queries in the tutorial, mention them in the comment section.