辗转相除法求最大公约数

       public static void CalcGCD(int largeNumber, int smallNumber, out int GCD)
        {
            GCD = 1;
            int remain = -1;
            while (remain != 0)
            {
                remain = largeNumber % smallNumber;
                GCD = smallNumber;
                largeNumber = smallNumber;
                smallNumber = remain;
            }
        }