C++ Program to Find the GCD and LCM of n Numbers

C++Server Side ProgrammingProgramming

This is the code to find out the GCD and LCM of n numbers. The GCD or Greatest Common Divisor of two or more integers, which are not all zero, is the largest positive integer that divides each of the integers. GCD is also known as Greatest Common Factor.

The least common multiple (LCM) of two numbers is the smallest number (not zero) that is a multiple of both numbers.


   Take two numbers as input
   Call the function gcd() two find out gcd of n numbers
   Call the function lcm() two find out lcm of n numbers
   gcd(number1, number2)
   Declare r, a, b
   Assign r=0
   a = (number1 greater than number2)? number1: number2
   b = (number1 less than number2)? number1: number2
   r = b
   While (a mod b not equal to 0)
         r = a mod b
      Return r
   lcm(number1, number2)
   Declare a
   a=(number1 greater than number2)?number1:number2
   While(true) do
      (a mod number1 == 0 and a number2 == 0)
      Return a
      Increment a

Example Code

using namespace std;
int gcd(int m, int n) {
   int r = 0, a, b;
   a = (m > n) ? m : n;
   b = (m < n) ? m : n;
   r = b;
   while (a % b != 0) {
      r = a % b;
      a = b;
      b = r;
   return r;
int lcm(int m, int n) {
   int a;
   a = (m > n) ? m: n;
   while (true) {
      if (a % m == 0 && a % n == 0)
         return a;
int main(int argc, char **argv) {
   cout << "Enter the two numbers: ";
   int m, n;
   cin >> m >> n;
   cout << "The GCD of two numbers is: " << gcd(m, n) << endl;
   cout << "The LCM of two numbers is: " << lcm(m, n) << endl;
   return 0;


Enter the two numbers:
The GCD of two numbers is: 1
The LCM of two numbers is: 42
Updated on 30-Jul-2019 22:30:25