HCF/GCD of Two Numbers Program in C++

To find the HCF of two numbers in C++, take any of the two numbers in hcf, and other number in a temp variable. Decrement the largest of these two by the other until the values in these two variables are same. When they are same, we have HCF in both of these variables.

In the following program, we read two numbers to n1 and n2, and find their HCF.

C++ Program

#include <iostream>
using namespace std;

int main() {
    int n1, n2;
    cout << "Enter first number : ";
    cin >> n1;
    cout << "Enter second number : ";
    cin >> n2;
    int hcf = n1, temp = n2;
    while(hcf != temp) {
        if(hcf > temp)
            hcf = hcf - temp;
            temp = temp - hcf;
    cout << "HCF : " << hcf << endl;


Enter first number : 15
Enter second number : 10
HCF : 5
Program ended with exit code: 0
Enter first number : 12
Enter second number : 16
HCF : 4
Program ended with exit code: 0


In this C++ Tutorial, we learned how to find HCF of two numbers in C++, with example program.