C program to find GCD of numbers using recursive function

Problem

Find the greatest common divisor (GCD) for the given two numbers by using the recursive function in C programming language.

Solution

The solution to find the greatest common divisor (GCD) for the given two numbers by using the recursive function is as follows −

Algorithm

Refer an algorithm given below to find the greatest common divisor (GCD) for the given two numbers by using the recursive function.

Step 1 − Define the recursive function.

Step 2 − Read the two integers a and b.

Step 3 − Call recursive function.

a. if i>j
b. then return the function with parameters i,j
c. if i==0
d. then return j
e. else return the function with parameters i,j%i.

Flow chart

A flowchart is given below for an algorithm to find the greatest common divisor (GCD) for the given two numbers by using the recursive function.

Example

Following is the C program to find the greatest common divisor (GCD) for the given two numbers by using the recursive function −

#include<stdio.h>
#include<math.h>
unsigned int GCD(unsigned i, unsigned j);
int main(){
   int a,b;
   printf("Enter the two integers: \n");
   scanf("%d%d",&a,&b);
   printf("GCD of %d and %d is %d\n",a,b,GCD(a,b));
   return 0;
}
/* Recursive Function*/
unsigned int GCD(unsigned i, unsigned j){
   if(j>i)
      return GCD(j,i);
   if(j==0)
      return i;
   else
      return GCD(j,i%j);
}

Output

When the above program is executed, it produces the following result −

Enter the two integers: 4 8
GCD of 4 and 8 is 4