6.31 C++ How to Program (8th Edition) By Paul Deitel, Harvey Deitel

(Greatest Common Divisor) The greatest common divisor (GCD) of two integers is the largest integer that evenly divides each of the numbers. Write a function gcd that returns the greatest common divisor of two integers.

Solution:

#include <iostream>
using std::cout;
using std::cin;
using std::endl;
 
int gcd1(int, int);
 
int main()
{
   int a, b;
 
   cout << "Enter two integers: ";
   cin >> a >> b;
   cout << "GCD (Euclidian) is " << gcd1(a, b) << endl;
 
   return 0;
}
 
//Euclidian
int gcd1(int a, int b)
{
   if(a == b)
      return a;
 
   while(b!= 0 || a!= 0)
   {
      if( b != 0)
      {
         a %= b;
      }
      else
         return a;
 
      if( a != 0)
      {
         b %= a;
      }
      else
         return b;
   }
 
}