计算e号C＃

Question

我试图计算e数

e = 1 + (1/1! + 1/2! + 1/3! + ..)

用户将在该表单上选择试验次数。 形成

 int trialNumber = Convert.ToInt32(Math.Round(trialNumberForm.Value, 0));
        int factorial = trialNumber;
        float factResult = 0;

        for (int i = 1; i < trialNumber; i++)
        {

            for (int b = 1; b < i; b++) //calculates x! here.
            {
                factorial = factorial * b;


            }
           factResult = factResult + (1 / factorial);
        }
        factResult++;
        MessageBox.Show(factResult.ToString());

它会计算您选择的结果1！ 我试图将变量类型从double更改为float但是没有修复它。 如何根据我上面写的公式对数字采取行动？

Answer 1

你根本不需要因子（具有整数除法和整数溢出问题）

  1/(n+1)! == (1/n!)/(n+1)

您可以轻松实现e计算

  double factResult = 1; // turn double into float if you want
  double item = 1;       // turn double into float if you want

  for (int i = 1; i < trialNumber; ++i)
    factResult += (item /= i);

  ...

  MessageBox.Show(factResult.ToString());

成果：

   trial number | e
   -------------------------------
              1 | 1
              2 | 2
              3 | 2.5
              4 | 2.666666... 
              5 | 2.708333...
             10 | 2.71828152557319
             15 | 2.71828182845823 
             20 | 2.71828182845905

Answer 2

正如@kabdulla和@ScottChamberlain所说，你正在进行整数除法，你需要一个浮点除法：

for (int b = 1; b < i; b++) //calculates x! here.
{
    factorial = factorial * b;
}
factResult = factResult + (1 / factorial);

应该

for (int b = 2; b < i; b++) //calculates x! here.
{
    factorial = factorial * b;
}
factResult = factResult + (1.0 / factorial);

另外，我在b = 2开始for循环，因为乘以1是没用的。