Program to Find LCM of Two Numbers - C, C++ Code

Write a program to find LCM of two numbers in C, C++. Given two numbers a and b, we have to write a code to find LCM of a and b.

In this tutorial, we cover following topics.

• What is LCM?
• Program to find LCM of two numbers in C++
• Program to find LCM of two numbers in C

What is LCM (Least Common Multiple)?

The LCM of two numbers is the smallest number that is divisible by both numbers.

For example -

LCM(8, 16) - Least common multiple of 8 and 16 is 16.

Multiples of 8 are :

8, 16, 24, 32 .......

Multiples of 16 are :

16, 32, 48, 64 .......

Common multiples of 8 and 16 are :

16, 32, 64 ..........

So, the least common multiple (LCM) of 8 and 16 are 16.

Formula to calculate LCM(a, b) = (a * b) / GCD(a, b)

In my previous post, i have already discussed and explained the program to find GCD of two numbers using Recursion.

Program to Find LCM of Two Numbers in C++

#include <iostream>
using namespace std;

int gcd(int a, int b) {
 
    if(b == 0){
       return a;
    }
 
    return gcd(b , a%b);
}

int lcm(int a, int b) {
 
    return (a*b)/gcd(a, b); 
}

int main() {
 
    int a, b, result;
 
    // Input
    cout << "Enter two numbers \n";
    cin  >> a >> b;
 
    // Method call to calculate LCM
    result = lcm(a, b);
 
    cout << " LCM of " << a << " and " << b << " is " << result;
    return 0;
}

Program to Find LCM of Two Numbers in C

#include <stdio.h>

int gcd(int a, int b) {
 
    if(b == 0){
      return a;
    }
 
    return gcd(b , a%b);
}

int lcm(int a, int b) {
 
    return (a*b)/gcd(a, b); 
}

int main() {
 
    int a, b, result;
 
    printf("Enter two numbers \n");
    scanf( "%d%d", &a, &b);
 
    result = lcm(a, b);
 
    printf("LCM of %d and %d is %d", a, b, result);
 
    return 0;
}

Output :

Enter two numbers :   3,   5

LCM of 3 and 5 is  15

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