Net中随机函数的算法

以前写程序的时候，经常用到随机函数。不过也就事随手拿了一用完成目的而已。不知道今天怎么了特别想看看随机函数的算法是怎么回事。于是结合

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归纳了一下：

using System;

    class MyRnd

    ...{

        private const int MBIG = Int32.MaxValue;

        private const int MSEED = 161803398;

        private const int MZ = 0;

        private int inext, inextp;

        private int[] SeedArray = new int[56];

        public MyRnd()

            : this(Environment.TickCount)

        //一个 32 位带符号整数，它包含自上次启动计算机以来所经过的时间（以毫秒为单位）。

        ...{

        }

        public MyRnd(int Seed)

            int ii;

            int mj, mk;

            //Initialize our Seed array.

            //This algorithm comes from Numerical Recipes in C (2nd Ed.)

            mj = MSEED - Math.Abs(Seed);

            SeedArray[55] = mj;

            mk = 1;

            for (int i = 1; i &lt; 55; i++)

            ...{  //Apparently the range [1..55] is special (Knuth) and so we're wasting the 0'th position.

                ii = (21 * i) % 55;

                SeedArray[ii] = mk;

                mk = mj - mk;

                if (mk &lt; 0) mk += MBIG;

                mj = SeedArray[ii];

            }

            for (int k = 1; k &lt; 5; k++)

            ...{

                for (int i = 1; i &lt; 56; i++)

                ...{

                    SeedArray[i] -= SeedArray[1 + (i + 30) % 55];

                    if (SeedArray[i] &lt; 0)

                        SeedArray[i] += MBIG;

                }

            inext = 0;

            inextp = 21;

            Seed = 1;

        //产生0~1的double数

        protected virtual double Sample()

            int retVal;

            int locINext = inext;

            int locINextp = inextp;

            if (++locINext &gt;= 56) locINext = 1;

            if (++locINextp &gt;= 56) locINextp = 1;

            retVal = SeedArray[locINext] - SeedArray[locINextp];

            if (retVal &lt; 0) retVal += MBIG;

            SeedArray[locINext] = retVal;

            inext = locINext;

            inextp = locINextp;

            return (retVal * (1.0 / MBIG));

        public virtual double NextDouble()

            return Sample();

         public virtual int Next(int minValue, int maxValue) ...{

           if (minValue&gt;maxValue) ...{

               throw new ArgumentOutOfRangeException("Argument_MinMaxValue");

           }

           int range = (maxValue-minValue);

           //This is the case where we flipped around (e.g. MaxValue-MinValue);

           if (range&lt;0) ...{

               long longRange = (long)maxValue-(long)minValue;

               return (int)(((long)(Sample()*((double)longRange)))+minValue);

           return ((int)(Sample()*(range)))+minValue;

       }

    }

使用方法：

static void Main(string[] args)

            MyRnd r = new MyRnd();

            Console.WriteLine(r.NextDouble().ToString());

            Console.Read();