Binary GCD

gistfile1.txt

unsigned int gcd(unsigned int u, unsigned int v)
{
    // simple cases (termination)
    if (u == v)
        return u;

    if (u == 0)
        return v;

    if (v == 0)
        return u;

    // look for factors of 2
    if (~u & 1) // u is even
        if (v & 1) // v is odd
            return gcd(u >> 1, v);
        else // both u and v are even
            return gcd(u >> 1, v >> 1) << 1;

    if (~v & 1) // u is odd, v is even
        return gcd(u, v >> 1);

    // reduce larger argument
    if (u > v)
        return gcd(u - v, v);

    return gcd(v - u, u);
}

int findGCD(int arr[], int n) 
{ 
    int result = arr[0]; 
    for (int i = 1; i < n; i++) 
    { 
        result = gcd(arr[i], result); 
  
        if(result == 1) 
        { 
           return 1; 
        } 
    } 
    return result; 
}