a answer to http://www.weibo.com/1560442584/z3MQEgZbC?type=repost

Random Words

----------------------------------Unsafe Code---------------------

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace WordsRandom
{
    class Program
    {

        static  void Main(string[] args)
        {
            do
            {
                var str = Console.ReadLine();
                RandomWords(str);
                Console.WriteLine(str);
            } while (true);

        }


        public struct Pair<TX, TY>
        {
            public TX X;
            public TY Y;

        }
        public struct Pair
        {
            public static Pair<TX, TY> Create<TX, TY>(TX x, TY y)
            {
                return new Pair<TX, TY> { X = x, Y = y };
            }
        }
        static Random _rnd = new Random();
        static HashSet<char> _splitChars = new HashSet<char> { '\'', '.', ' ', '\r', '\t', '\n' };
        static unsafe void  RandomWords(string content)
        {

            var spaceMarks = System.Linq.Enumerable.Concat(" ", content).Concat(" ")
                .Select((c, i) => Pair.Create(c, i-1))
                .Where(p => _splitChars.Contains(p.X))
                .Select(p => p.Y);


            var segs = spaceMarks
                .Zip(spaceMarks.Skip(1), (x, y) => Pair.Create(x+ 2, y-x-3))       //对空格进行两两配对计算混淆的起止坐标
                   .Where(p => p.Y > 1);                                   //没有内容可混淆的过滤掉

            fixed (char* ptr = content)
            {
                foreach (var seg in segs)
                {
                    RandomArea(seg, ptr);
                }
            }
          
        }

        static unsafe public void RandomArea(Pair<int, int> marks, char* array)
        {
            //   var chars = new char[segment.Count];
            int Offset = marks.X;
            int Count = marks.Y;


            for (int i = 0; i < Count; i++)
            {
                char tempChar;
                var remains = Count - i;//随着循环进行，可以取出的范围减少

                var last = remains + Offset - 1;
                //随机取出一个  和剩余没有抽取的最后元素交换。最后的元素们就是结果
                var chosen = _rnd.Next(0, remains) + Offset;
                tempChar = array[chosen];
                array[chosen] = array[last];
                array[last] = tempChar;
            }

        }


    }
}




-----------------------------------Safe Managed code------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WordsRandom
{
    class Program
    {

        static void Main(string[] args)
        {
            do
            {
                var str = Console.ReadLine();

                Console.WriteLine(RandomWords(str));
            } while (true);

        }


        public struct Pair<TX, TY>
        {
            public TX X;
            public TY Y;

        }
        public struct Pair
        {
            public static Pair<TX, TY> Create<TX, TY>(TX x, TY y)
            {
                return new Pair<TX, TY> { X = x, Y = y };
            }
        }
        static Random _rnd = new Random();
        static HashSet<char> _splitChars = new HashSet<char> { '\'', '.', ' ', '\r', '\t', '\n' };
        static public string RandomWords(string content)
        {
            var charArray = new Char[content.Length + 2];
            content.CopyTo(0, charArray, 1, content.Length);
            charArray[0] = ' ';
            charArray[charArray.Length - 1] = ' ';

            //标记所有空格
            var spaceMarks = charArray
                .Select((c, i) => Pair.Create(c, i))
                .Where(p => _splitChars.Contains(p.X))
                .Select(p => p.Y);


            var segs = spaceMarks
                .Zip(spaceMarks.Skip(1), (x, y) => Pair.Create(x, y))       //对空格进行两两配对
                .Select(p => Pair.Create(p.X + 2, p.Y - p.X - 3))           //计算混淆的起止坐标
                .Where(p => p.Y > 1)                                        //没有内容可混淆的过滤掉
                .Select(p => new ArraySegment<Char>(charArray, p.X, p.Y));


            foreach (var seg in segs)
            {
                RandomArea(seg);
            }


            return new string(charArray, 1, charArray.Length - 2);
        }

        static public void RandomArea(ArraySegment<char> segment)
        {
            //   var chars = new char[segment.Count];

            for (int i = 0; i < segment.Count; i++)
            {
                char tempChar;
                var remains = segment.Count - i;//随着循环进行，可以取出的范围减少

                var last = remains + segment.Offset - 1;
                //随机取出一个  和剩余没有抽取的最后元素交换。最后的元素们就是结果
                var chosen = _rnd.Next(0, remains) + segment.Offset;
                tempChar = segment.Array[chosen];
                segment.Array[chosen] = segment.Array[last];
                segment.Array[last] = tempChar;
            }

        }
    }
}