学步园

前一篇说到根据指定概率抽奖，又查阅了一些资料，发现一般都这么实现。不过由于产生0-1之间的double问题，对程序作了修改。产生随机数作了简单修改。然后将概率不再作为小数，而是扩大为基数倍。
先看工具类：

public static class ToolMethods
    {
        /// <summary>
        /// 获取概率的基数
        /// </summary>
        /// <param name="array"></param>
        /// <returns></returns>
        public static long GetBaseNumber(double[] array)
        {
            long result = 0;


            try
            {
                if (array == null || array.Length == 0)
                {
                    return result;
                }


                string targetNumber = string.Empty ;


                foreach (double item in array)
                {
                    string temp = item.ToString();


                    if (!temp.Contains('.'))
                    {
                        continue;
                    }


                    temp = temp.Substring(temp.IndexOf('.')).Replace(".", "");


                    if (targetNumber.Length < temp.Length)
                    {
                        targetNumber = temp;
                    }
                }


                if (!string.IsNullOrEmpty(targetNumber))
                {
                    int ep = targetNumber.Length;


                    result = (long)Math.Pow(10, ep);
                }
            }
            catch { }


            return result;
        }


        /// <summary>
        /// 获取随机数
        /// </summary>
        /// <param name="random"></param>
        /// <param name="min"></param>
        /// <param name="max"></param>
        /// <returns></returns>
        public static long GetRandomNumber(this Random random, long min, long max)
        {
            byte[] minArr = BitConverter.GetBytes(min);


            int hMin = BitConverter.ToInt32(minArr, 4);


            int lMin = BitConverter.ToInt32(new byte[] { minArr[0], minArr[1], minArr[2], minArr[3] }, 0);


            byte[] maxArr = BitConverter.GetBytes(max);


            int hMax = BitConverter.ToInt32(maxArr, 4);


            int lMax = BitConverter.ToInt32(new byte[] { maxArr[0], maxArr[1], maxArr[2], maxArr[3] }, 0);


            if (random == null)
            {
                random = new Random();
            }


            int h = random.Next(hMin, hMax);


            int l = 0;


            if (h == hMin)
            {
                l = random.Next(Math.Min(lMin, lMax), Math.Max(lMin, lMax));
            }
            else
            {
                l = random.Next(0, Int32.MaxValue);
            }


            byte[] lArr = BitConverter.GetBytes(l);


            byte[] hArr = BitConverter.GetBytes(h);


            byte[] result = new byte[8];


            for (int i = 0; i < lArr.Length; i++)
            {
                result[i] = lArr[i];
                result[i + 4] = hArr[i];
            }


            return BitConverter.ToInt64(result, 0);
        }
    }

主要是取随机数和获得当前概率的基数。
抽奖程序，作了一些调整。

class Program
    {
        static void Main(string[] args)
        {
            List<KeyValuePair<long, double>> elements = new List<KeyValuePair<long, double>>();


            elements.Add(new KeyValuePair<long, double>(0, 0.000002));


            elements.Add(new KeyValuePair<long, double>(1, 0.000004));


            elements.Add(new KeyValuePair<long, double>(2, 0.0001));


            elements.Add(new KeyValuePair<long, double>(3, 0.0001));


            elements.Add(new KeyValuePair<long, double>(4, 0.0003));


            elements.Add(new KeyValuePair<long, double>(5, 0.000004));


            elements.Add(new KeyValuePair<long, double>(6, 0.000004));


            elements.Add(new KeyValuePair<long, double>(7, 0.00016));


            elements.Add(new KeyValuePair<long, double>(8, 0.000008));


            elements.Add(new KeyValuePair<long, double>(9, 0.00012));


            elements.Add(new KeyValuePair<long, double>(10, 0.0));


            elements.Add(new KeyValuePair<long, double>(11, 0.999198));


            Dictionary<long, string> prize = new Dictionary<long, string>();


            prize.Add(0, @"奖品1");


            prize.Add(1, @"奖品2");


            prize.Add(2, @"奖品3");


            prize.Add(3, @"奖品4");


            prize.Add(4, @"奖品5");


            prize.Add(5, @"奖品6");


            prize.Add(6, @"奖品7");


            prize.Add(7, @"奖品8");


            prize.Add(8, @"奖品9");


            prize.Add(9, @"奖品10");


            prize.Add(10, @"奖品11");


            prize.Add(11, @"谢谢参与！");


            //求出概率基数


            long basicNumber = 0;


            double[] array = new double[elements.Count];


            int m=0;


            foreach (KeyValuePair<long, double> item in elements)
            {
                array[m] = item.Value;


                m++;
            }


            basicNumber = ToolMethods.GetBaseNumber(array);




            //判断设置的概率
            double allRate = 0;


            foreach (var item in elements)
            {
                allRate += item.Value;
            }


            if (allRate != 1)
            {
                Console.WriteLine("奖品概率设置错误！");


                Console.WriteLine(allRate);


                Console.ReadLine();


                return;
            }


            //抽奖
            Random random = new Random();


            long selectedElement = 0;


            while (true)
            {
                for (int n = 0; n < 20; n++)
                {
                    long diceRoll = ToolMethods.GetRandomNumber(random,1,basicNumber);


                    long cumulative = 0;


                    for (int i = 0; i < elements.Count; i++)
                    {
                        cumulative += (long)(elements[i].Value * basicNumber);


                        if (diceRoll <= cumulative)
                        {
                            selectedElement = elements[i].Key;


                            break;
                        }
                    }


                    Console.WriteLine(prize[selectedElement]);
                }


                string read = Console.ReadLine();


                if (read=="e")
                {
                    break;
                }
            }


            Console.ReadLine();
        }
    }

这样一来，概率设置的低一般是不会中奖的。如图，

代码下载