c++ - 如何重置for循环中的值？

Question

我需要帮助找出我的代码哪里出错了。我想重置循环的值，以便它不会编译，因为我现在的输出在当前计算中使用过去的输入值，而我希望输出每次都不同，就好像这是第一次运行代码一样。当我不使用 while 循环时代码工作正常，但每次我都必须重新运行程序。我希望输出每次都提示新输入，但不在新计算中使用过去的输入。我知道我解释得不是很好，但我有点迷路了。任何帮助!

这是我的问题:

An approximate value of pi can be calculated using the series given below:

pi = 4 · [ 1 – 1/3 + 1/5 – 1/7 + 1/9 ... + (–1 ^ n)/(2n + 1) ]

Write a C++ program to calculate the approximate value of pi using this series. The program takes an input n that determines the number of terms in the approximation of the value of pi and outputs the approximation. Include a loop that allows the user to repeat this calculation for new values n until the user says she or he wants to end the program.

#include <cstdio>
#include <iostream>

using namespace std;

int main()
{
  int n;
  double sum=0;

  cout << "Enter the number of terms to approximate (or zero to quit):\n";
  cin >> n;

  if (n == 0)
    {
   return 0;
    }

  while (n != 0)
   {
     { for(int i=0;i<n;i++)
       {
         if (i%2==0)
           {
             sum += 1.0/(2*i+1);
           }
         else
           {
             sum += -1.0/(2*i+1);
           }
       }

    cout.setf(ios::showpoint);
    cout.precision(3);
    cout << "The approximation is " << sum*4 << " using " << n << " terms." << endl;
     }
    cout << "Enter the number of terms to approximate (or zero to quit):\n";
    cin >> n;
    }

return 0;
}

这是我的输出:

输出应该是这样的:

Answer 1

在进入for 循环之前，您不要重置sum。只需添加

sum=0;

在 for 行之前。