题目：输入一个数，然后将这个数字的各个位置重新排列，找出最小的数，但是不能以0开头
比如：输入201，那么最小的数字为102；
思路：先判断是正数还是负数，如果是正数，把这个数字各个位置都拆分，存到数组中去，然后对这个数据进行排序，首先找出非零的最小数字，然后再看有几个零，就在最小数字后面加上几个零，后面的数组，根据排序数组中的数依次的从小到大添加。负数的话，道理也是一样。

        public static void Main(string[] args)
        {
            Console.Write("输入一个数：");
        string numberStr = Console.ReadLine();
            long number = Convert.ToInt64(numberStr);
            Console.WriteLine(caulate(number));
        }
     static long caulate(long longKeys)
        {
            if (longKeys > 0)
                return (long)caulateZ(longKeys);
            else
                return (long)caulateF(-longKeys);
        }

        static long caulateZ(long longKeys)
        {
            long minNum = 0;
            int length = longKeys.ToString().Length;
            int [] tmp = new int[length];
            int index = 0;
            while(longKeys/10 != 0)
            {
                tmp[index] = (int)longKeys % 10;
                longKeys = longKeys / 10;
                index++;
            }
            tmp[length - 1] = (int)longKeys;
            Array.Sort(tmp);
            int lengthZero = 0;
            for (int i = 0; i < tmp.Length;i++)
            {
                if(tmp[i] == 0)
                {
                    lengthZero++;
                }
                else{
                    break;
                }
            }
            minNum = tmp[lengthZero];
            for (int i = 0; i < tmp.Length-1; i++)
            {
                if (i < lengthZero)
                {
                    minNum *= 10;
                    
                }else{
                    lengthZero++;
                    minNum = minNum * 10 + tmp[lengthZero];
                }
            }

            return minNum;
        }

        static long caulateF(long longKeys)
        {
            long minNum = 0;
            int length = longKeys.ToString().Length;
            int[] tmp = new int[length];
            int index = 0;
            while (longKeys / 10 != 0)
            {
                tmp[index] = (int)longKeys % 10;
                longKeys = longKeys / 10;
                index++;
            }
            tmp[length - 1] = (int)longKeys;
            Array.Sort(tmp);
            int lengthZero = 0;
            for (int i = 0; i < tmp.Length; i++)
            {
                if (tmp[i] == 0)
                {
                    lengthZero++;
                }
                else
                {
                    break;
                }
            }
            minNum = tmp[tmp.Length - 1];

            for (int i = tmp.Length-2; i >= 0; i--)
            {
                if (i < lengthZero)
                {
                    minNum *= 10;
                }
                else
                {
                    minNum = minNum * 10 + tmp[i];
                }
            }

            return 0-minNum;
        }