C# 二分查找求平方根

       static int Sqrt1(int num)
        {
            if (num < 0)
            {
                throw new Exception(num + " doesn't have square root.");
            }

            if (num == 1)
            {
                return num;
            }
            int low = 0;
            int high = num;
            int temp = (low + high) / 2;
            int sign = temp;
            checked
            {
                while (Math.Abs(temp * temp - num) > 1)
                {
                    sign = temp;
                    if (temp * temp > num)
                    {
                        high = temp;
                    }
                    else
                    {
                        low = temp;
                    }
                    temp = (low + high) / 2;
                    if (sign == temp)
                    {
                        break;
                    }
                }
            }
            if (temp * temp == num)
            {
                return temp;
            }
            else
            {
                throw new Exception(num + " doesn't have integer square root.");
            }
        }