C Exercises: Find GCD of two numbers

C Recursion : Exercise-7 with Solution

Write a program in C to find the GCD of two numbers using recursion.

Pictorial Presentation:

Sample Solution:

C Code:

#include<stdio.h>

int findGCD(int num1,int num2);
int main()
{
  int num1,num2,gcd;
  printf("\n\n Recursion : Find GCD of two numbers :\n");
  printf("------------------------------------------\n");  
  printf(" Input 1st number: ");
  scanf("%d",&num1);
  printf(" Input 2nd number: ");
  scanf("%d",&num2);
  
  gcd = findGCD(num1,num2);
  printf("\n The GCD of %d and %d is: %d\n\n",num1,num2,gcd);
  return 0;
}

int findGCD(int a,int b)
{
     while(a!=b)
     {
          if(a>b)
              return findGCD(a-b,b);
          else
             return findGCD(a,b-a);
     }
     return a;
}

Sample Output:

 Recursion : Find GCD of two numbers :                                                                        
------------------------------------------                                                                    
 Input 1st number: 10                                                                                         
 Input 2nd number: 50                                                                                         
                                                                                                              
 The GCD of 10 and 50 is: 10

Explanation:

int findGCD(int a,int b)
{
     while(a!=b)
     {
          if(a>b)
              return findGCD(a-b,b);
          else
             return findGCD(a,b-a);
     }
     return a;
}

This function findGCD() takes two integers as parameters (int a, int b) and repeatedly subtracts the smaller number from the larger number until they become equal. When they become equal, the function returns the value of either one of them as the GCD.

Flowchart:

C Programming Code Editor:

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