int fermat(int n)
{
    int result;

    do {    
        int x = (int)ceil(sqrt(0.0+n));
        int y = x*x - n;
    
        while(!issqrt(y)){
            y = y + 2*x + 1;
            x += 1;
        }
        // This method could easely
        // return the other prime too
        // (x-sqrt(y));
        result = int(x+sqrt(0.0+y)+0.5);
    } while(result == n);

    return result;
}

• 这个 pollard_p-1 (841) sunmoonstar_love 2005-08-17 23:32:55