What is the fastest way to find the GCD of two numbers?

Question

I have an array of size n. I need to find the GCD of each element with a given number and if it\'s greater than 1, add it to another array. What\'s the fastest way to do thi

Answer 1

#include
int main()
{
   int a,b,a1,b1;
   printf("Enter two numbers:");
   scanf("%d%d",&a,&b);
   a1=a;b1=b;
   while(a!=b)
   {
      if(a>b)
        a=a-b;
      else
        b=b-a;
   }
   printf("GCD of %d and %d is %d\n",a1,b1,a);
   printf("LCM of %d and %d is %d",a1,b1,(a1*b1/a));
}