class Program  {    static void Main(string[] args)    {      //初始化要發起的紅包基礎數據      double total = 100;      int num = 50;      double min = 0.01;      string temp;      bool flag = false;      Console.WriteLine(string.Format("是否需要自定義紅包金額和數量（默認{0}元/{1}人）Y/N：", total, num));      temp = Console.ReadLine();      if (temp.Trim().ToLower().Equals("y") || temp.Trim().ToLower().Equals("yes"))      {        Console.WriteLine("請輸入你要發起的紅包金額：");        do        {          temp = Console.ReadLine();          flag = double.TryParse(temp, out total);          if (!flag)          {            Console.WriteLine("金額必須為整數或小數，請重新輸入：");          }        } while (!flag);        Console.WriteLine("請輸入你要發起的紅包個數：");        do        {          temp = Console.ReadLine();          flag = int.TryParse(temp, out num);          if (!flag)          {            Console.WriteLine("紅包個數必須為整數，請重新輸入：");          }        } while (!flag);      }      total -= min * num;      if (total < 0)      {        Console.WriteLine("抱歉，你的金額不足！");        return;      }      //產生正態分布的隨機紅包金額，并計算相關的金額和數量保證數據的準確性      double average = total / num;      double variance = 1;      Random u1 = new Random();      Random u2 = new Random();      double[] nums = new double[num];      for (int i = 0; i < num; i++)      {        double? result = total;        if (i < num - 1 && total > 0)        {          do          {            result = Round((double)Normal(u1.NextDouble(), u2.NextDouble(), average, variance), 2);          } while (result == null || result < 0);          if (total > result)          {            total = (double)Round((total - (double)result), 2);          }          else          {            result = total;            total = 0;          }        }        else if (i == num - 1)        {          total = 0;        }        nums[i] = Math.Round(min + (double)result, 2); //浮點運算問題，這里需要四舍五入數據才正確        Console.WriteLine(string.Format("第{0}個紅包金額：{1}", i + 1, (min + result)));        Console.WriteLine("剩余金額：" + ((i != num - 1 && total == 0) ? min * (num - i - 1) : total + (min * (num - i - 1))));      }      Console.WriteLine("最大金額：" + nums.Max());      Console.WriteLine("最小金額：" + nums.Min());      Console.WriteLine("總額：" + Round(nums.Sum(), 2));      Console.WriteLine("初始方差：" + variance);      Console.WriteLine("結果方差：" + Variance(nums));      Console.WriteLine("按任意鍵退出！");      Console.ReadKey();    }    /// <summary>    /// 產生符合正態分布的隨機數    /// </summary>    /// <param name="u1">正態分布第一個隨機數</param>    /// <param name="u2">正態分布第二個隨機數</param>    /// <param name="averageValue">正態期望(平均值)</param>    /// <param name="variance">正態標準差(Math.Sqrt(方差))</param>    /// <returns></returns>    public static double? Normal(double u1, double u2, double averageValue, double variance)    {      double? result = null;      try      {        result = averageValue + Math.Sqrt(variance) * Math.Sqrt((-2) * Math.Log(u1)) * Math.Sin(2 * Math.PI * u2);      }      catch (Exception)      {        result = null;      }      return result;    }    /// <summary>    /// 求一組數據的方差    /// </summary>    /// <param name="list">要求的數組</param>    /// <returns></returns>    public static double Variance(double[] nums)    {      double average = nums.Sum() / nums.Length;      double sum = 0;      double variance = 0;      foreach (double num in nums)      {        sum += Math.Pow((num - average), 2);      }      variance = sum / nums.Length;      return variance;    }    /// <summary>    /// 截取小數指定小數位，且不四舍五入    /// </summary>    /// <param name="originNum">要截取的小數</param>    /// <param name="lastNum">截取小數后位數</param>    /// <returns></returns>    public static double? Round(double originNum, int lastNum)    {      double? result = null;      int index = originNum.ToString().IndexOf('.');      if (index != -1)      {        string temp = originNum.ToString();        result = Convert.ToDouble(temp.Substring(0, index + 1) + temp.Substring(index + 1, Math.Min(temp.Length - index - 1, lastNum)));      }      if (result == 0)      {        result = null;      }      else if (index == -1)      {        result = originNum;      }      return result;    }  }