C++ Program to Find LCM of Two Numbers

In this post, we will learn how to find the lcm of two numbers using C++ Programming language.

The LCM (Least Common Multiple) of two numbers a and b is the smallest positive integer that is perfectly divisible by both a and b.

We will be finding the lcm of two numbers using the following ways:

  1. Using Standard Method
  2. Using GCD

So, without further ado, let’s begin this tutorial.

C++ Program to Find LCM of Two Numbers

// C++ Program to Find LCM of Two Numbers
#include <iostream>
using namespace std;

int main(){
    int a, b, lcm;
    
    // Asking for input
    cout << "Enter the first number: ";
    cin >> a;
    cout << "Enter the second number: ";
    cin >> b;
    
    lcm = (a > b) ? a : b; //greatest of the two
    
    while(1){
        if ((lcm % a == 0) && (lcm % b == 0)){
            cout << "LCM of two numbers: " << lcm;
            break;
        }
        ++lcm;
    }
    return 0;
}

Output

Enter the first number: 12
Enter the second number: 15
LCM of two numbers: 60

How Does This Program Work ?

    int a, b, lcm;

In this program, we have declared three int data type variables named a, b and lcm.

    // Asking for input
    cout << "Enter the first number: ";
    cin >> a;
    cout << "Enter the second number: ";
    cin >> b;

Then, the user is asked to enter two integers. The value of these two integers will get stored in a and b named variables.

    while(1){
        if ((lcm % a == 0) && (lcm % b == 0)){
            cout << "LCM of two numbers: " << lcm;
            break;
        }
        ++lcm;
    }

Now, we check whether the maximum value is divisible by both a and b or not. If yes, then the value of lcm variables is printed and our program terminates.

If not, then lcm is incremented by 1 and the same process goes on until lcm is exactly divisible by both a and b.

C++ Program to Find LCM of Two Numbers Using HCF

// C++ Program to Find the LCM of Two Numbers Using HCF
#include <iostream>
using namespace std;

int main(){
    int a, b, i, gcd, lcm;
    
    // Asking for input
    cout << "Enter the first number: ";
    cin >> a;
    cout << "Enter the second number: ";
    cin >> b;
    
    // Calculating GCD
    for (i = 1; i <= a && i <= b; ++i){
        if (a % i == 0 && b % i == 0)
        gcd = i;
    }
    
    // Calculating lcm using hcf
    lcm = (a * b) / gcd;
    cout << "LCM of two numbers: " << lcm << endl;
    return 0;
}

Output

Enter the first number: 3
Enter the second number: 5
LCM of two numbers: 15

Conclusion

I hope after going through this post, you understand how to find the lcm of two numbers using C++ Programming language.

If you have any doubt regarding the program, feel free to contact us in the comment section. We will be delighted to assist you.

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