增加分數的一系列的n次冪，並尋找求和 - C++

Question

我需要編寫一個程序，增加了1/^ 1 + 1/2^2 + 1/2^3和......讓用戶可以選擇輸入他們希望去的第n個術語。 （間2-10）

它需要顯示的級分（1/2 + 1/4 1/8 + ....）然後找出它們的和，並顯示在末端。 （1/2 + 1/4 1/8 + 1/16 + 1/32 + = 0.96875）

我錯過在我的代碼至關重要的東西，我不知道我做錯了。在程序將它們添加到一起之前，我會讓分數顯示多次。

// 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

你並不需要循環：

// 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; 
}