程序代码：

       //若大家手中有一些算法的话，不妨一起贴出来，大家往后看的时候也方便
      
        /// <summary>
        /// 折半查找
        /// </summary>
        /// <param name="arr">一维数组</param>
        /// <param name="num">查找的数字</param>
        /// <returns>对应数字的索引(数组中相同数字返回第一个的索引)，若不存在则值为-1</returns>
        public static int FindInHalf(int[] arr,int num)
        {
            int hight = arr.Length - 1, low = 0;
            int index = -1;
            while (low <= hight)
            {
                int middle = (hight + low) / 2;
                if (num == arr[middle])
                {
                    index = middle;
                    break;
                }
                else
                {
                    if (num < arr[middle])
                        hight = middle - 1;
                    else
                        low = middle + 1;
                }
            }
            return index;

        }

        /// <summary>
        /// 反转字符串
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        private static string RetStrBind(string str)
        {
            string result = "";
            for (int i = str.Length - 1; i >= 0; i--)
            {
                result += str[i];
            }
            return result;
        }

        /// <summary>
        /// 求一个整数是否是质数
        /// </summary>
        /// <param name="num"></param>
        /// <returns>true为否，fase为是</returns>
        private static bool GetPrime(int num)
        {
            bool rebool = false;
            for (int i = 2; i < num; i++)
            {
                rebool = num % i == 0;
                if (rebool)
                {
                    break;
                }
            }
            return rebool;
        }

        /// <summary>
        /// 求两个整数的最小公倍数
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns>最小公倍数</returns>
        public static int GetMultiple(int a, int b)
        {
            int mul=0;
            for (int i = (a > b) ? a : b; i <= a * b; i++)
            {
                if (i % a == 0 && i % b == 0)
                {
                    mul = i;
                    break;
                }
            }
            return mul;

        }

        /// <summary>
        /// 求两个整数的最大公约数
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns>最大公约数</returns>
        public static int GetDivisor(int a, int b)
        {
            int div = 0;
            for (int i = (a < b) ? a :b; i >= 1; i--)
            {
                if (a % i == 0 && b % i == 0)
                {
                    div = i;
                    break;
                }
            }
            return div;
        }