c++ - 将一系列分数的 n 次方相加并求和 - C++

Question

我需要编写一个程序来添加 1/2^1 + 1/2^2 + 1/2^3......并让用户可以选择输入他们想要的第 n 个术语去。 (2-10 之间)

它需要显示分数 (1/2 + 1/4 + 1/8....) 然后找出它们的总和并在最后显示。 (1/2 + 1/4 + 1/8 + 1/16 + 1/32 = .96875)

我在我的代码中遗漏了一些重要的东西，我不确定我做错了什么。在程序将它们加在一起之前，我让分数出现多次。

// This program displays a series of terms and computes its sum.
#include <iostream>
#include <cmath>
using namespace std;

int main()
{    
    int denom,              // Denominator of a particular term    
        finalTerm,    
        nthTerm;                 // The nth term
    double sum = 0.0;       // Accumulator that adds up all terms in the series

   // Calculate and display the sum of the fractions. 
   cout << "\nWhat should the final term be? (Enter a number between 2 and 10)";
   cin >> finalTerm;

   if (finalTerm >= 2 && finalTerm <= 10) 
   {   
        for (nthTerm = 1; nthTerm <= finalTerm; nthTerm++)
        {   
            denom = 2;
            while (denom <= pow(2,finalTerm))
            {   
                cout << "1/" << denom;
                denom *= 2;

                if (nthTerm < finalTerm)
                    cout << " + ";
                sum += pow(denom,-1);
            }   
        }   
        cout << " = " << sum;
   }   
   else
       cout << "Please rerun the program and enter a valid number.";

    cin.ignore();
    cin.get();

    return 0;
}  

Answer 1

你不需要 for 循环:

    // This program displays a series of terms and computes its sum.

#include <iostream>
#include <cmath>
using namespace std;

int main()
{    
    int denom,              // Denominator of a particular term    
        finalTerm,    
        nthTerm;                 // The nth term
    double sum = 0.0;       // Accumulator that adds up all terms in the series


   // Calculate and display the sum of the fractions. 
   cout << "\nWhat should the final term be? (Enter a number between 2 and 10)";
   cin >> finalTerm;

   if (finalTerm >= 2 && finalTerm <= 10) 
   {   
        //for (nthTerm = 1; nthTerm <= finalTerm; nthTerm++)
        //{ 
            denom = 2;
            while (denom <= pow(2,finalTerm))
            {   
                cout << "1/" << denom;
                denom *= 2;

                if (nthTerm < finalTerm)
                    cout << " + ";
                sum += pow(denom,-1);
            }   
        //} 
            cout << " = " << sum << endl;
   }   
   else
       cout << "Please rerun the program and enter a valid number.";

    cin.ignore();
    cin.get();

    return 0;
}