class Program
 {
  static void Main(string[] args)
  {
   //初始化要發(fā)起的紅包基礎數(shù)據(jù)
   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(shù)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(fā)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(shù)或小數(shù)，請重新輸入：");
     }
    } while (!flag);
    Console.WriteLine("請輸入你要發(fā)起的紅包個數(shù)：");
    do
    {
     temp = Console.ReadLine();
     flag = int.TryParse(temp, out num);
     if (!flag)
     {
      Console.WriteLine("紅包個數(shù)必須為整數(shù)，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(chǎn)生正態(tài)分布的隨機紅包金額，并計算相關的金額和數(shù)量保證數(shù)據(jù)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(shù)據(jù)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(chǎn)生符合正態(tài)分布的隨機數(shù)
  /// </summary>
  /// <param name="u1">正態(tài)分布第一個隨機數(shù)</param>
  /// <param name="u2">正態(tài)分布第二個隨機數(shù)</param>
  /// <param name="averageValue">正態(tài)期望(平均值)</param>
  /// <param name="variance">正態(tài)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(shù)據(jù)的方差
  /// </summary>
  /// <param name="list">要求的數(shù)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(shù)指定小數(shù)位，且不四舍五入
  /// </summary>
  /// <param name="originNum">要截取的小數(shù)</param>
  /// <param name="lastNum">截取小數(shù)后位數(shù)</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;
  }
 }