一个c#面试题

C#
给你一个string字符串， abcd as,ccd.dsa
反转这个字符串变为：   dsa.ccd,as abcd

要求：不能用【任何】【系统函数】。

实现代码如下：

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Text.RegularExpressions;





namespace ReverseString

{

    class Program

    {

        public static string ReverseString(String originalString)

        {

            if (string.IsNullOrWhiteSpace(originalString))

            {

                throw new ArgumentException("orginalString can not be null or white space");

            }

            char[] temp = originalString.ToCharArray();

            int begin = 0, end = temp.Length - 1;

            ReverseCharArray(temp, begin, end);



            Console.WriteLine(temp);



            int i = 0, j = 0;

            int k = 0;

            do

            {

                if (!char.IsLetter(temp[k]))

                {

                    j = k - 1;

                    ReverseCharArray(temp, i, j);

                    i = k + 1;

                }               

                k++;

            }

            while (k <= end);

            if (char.IsLetter(temp[end]))

            {

                ReverseCharArray(temp, i, end);

            }     

            string finalString = new string(temp);

            return finalString;



        }

        public static void ReverseCharArray(char[] charArray, int begin, int end)

        {

            while (begin < end)

            {

                char temp = charArray[begin];

                charArray[begin] = charArray[end];

                charArray[end] = temp;

                begin++;

                end--;

            }

        }



        static void Main(string[] args)

        {

            String originalString = "abcd as,ccd.dsa";

            String ouput = "dsa.ccd,as abcd";

            ReverseString(originalString);

            Console.ReadKey();

        }



    }

}