C program to find LCM and GCD using recursion

C program to find LCM and GCD using recursion of two integers entered by the user.

Please go through following C programming articles to understand the concept of the program.

• C programming functions
• C programming recursion
• C programming user-defined function

We have use following formula to find the LCM of two numbers using GCD

LCM = (number1 * number2) / GCD

Visit this page to learn how to calculate GCD using loops

C program to find GCD and LCM using recursion

#include <stdio.h>
int gcd(int x, int y);  //function prototype

int main()
{
   int num1, num2, hcf, lcm;

   printf("Enter two integer Values:\n");
   scanf("%d %d", &num1, &num2);

   hcf = gcd(num1, num2);
   printf("GCD: %d", hcf);
   printf("\nLCM: %d", (num1 * num2) / hcf);
   return 0;
}
//recursive function
int gcd(int x, int y)
{
   if (y == 0)   //recursion termination condition
   {
      return x;
   }
   else 
   {
      return gcd(y, x % y);   //calls itself
   }
}

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Output

Visit this page to learn how to calculate LCM using loops

Explanation

In the above program, recursive function gcd returns the value of gcd. The termination condition of the recursive function is y == 0 which checks whether the number is equal to zero or not.