查找用戶在C++中輸入的最大數字的平均值3

Question

因此設計問題是：

輸入3個數字並顯示最大值。繼續輸入3組數字，直到用戶想要退出。查找所有最大數字的平均值。

所以輸入數字能正常工作，但是當我試圖插入SENTINEL值來停止循環時，我需要爲所有3個數字輸入它，並且它不會給我輸入的過去數字的正確平均值。

任何幫助非常感謝您的時間！

#include <iostream> 
using namespace std; 

int main() 
{ 

    const int SENTINEL = -1; 
    int num1; 
    int num2 = 0; 
    int num3 = 0; 
    int largest; 
    int sum; 
    int count; 
    float average; 

    // initialize the count and sum 
    count = 0; 
    sum = 0; 

    while (num1 != SENTINEL) 
    { 

     // Prompt user for the first number or to quit 
     cout << "If you want to quit enter " << SENTINEL << " to stop\n " << endl; 
     cout << "Enter first number "; 
     cin >> num1; 

     // Prompt the user for the second number 
     cout << "please enter second number     "; 
     cin >> num2; 

     // Prompt the user for a third number 
     cout << "please enter the third number    "; 
     cin >> num3; 

     // Compare numbers 1 and 2 for the largest number 
     if (num1 > num2) 
     { 
      largest = num1; 
     } 
     else 
     { 
      largest = num2; 
     } 

     // Compare largest to last number input 
     if (num3 > largest) 
     { 
      largest = num3; 
     } 

     // Display the largest number 
     cout << "largest number is: " << largest << endl; 

     // Increment the count 
     count++; 

    } 



    if (count > 0) 
    { 
     average = sum/count; 
     cout << "Average of the numbers is " << average; 
    } 

    return 0; 
} 

Answer 1

輸入num1後立即有條件地破環。

cin >> num1; 
if (SENTINEL == num1) 
{ 
    break; 
} 

Answer 2

後

cin >> num1; 

您可以檢查，如果其SENTIEL數和從迴路斷線：

if (num1 == SENTIEL) 
    break 

，這樣就不會執行其他CIN的。

Answer 3

使用break;指令是一種可能性，但通常被認爲不夠優雅，難以維護。

原因是你打破了代碼的流程，你的程序的讀者（這可能不是你在大的程序中，或者如果你分享它）期望你的循環代碼繼續到它。如果你的函數有一個或幾個指令，可能很難理解函數的意圖，因爲你必須記住在哪些情況下循環已經結束。

解決你的問題的基本原則是在得到num1的值之後，在正確的地方開始你的循環。那麼你的循環也必須以它結束。這樣，在用戶鍵入num1後，您將始終檢查退出條件。

// initialize the count and sum 
count = 0; 
sum = 0; 

// Prompt user for the first number or to quit 
cout << "If you want to quit enter " << SENTINEL << " to stop\n " << endl; 
cout << "Enter first number "; 
cin >> num1; 

while (num1 != SENTINEL) 
{ 

    // Prompt the user for the second number 
    cout << "please enter second number     "; 
    cin >> num2; 

    // Prompt the user for a third number 
    cout << "please enter the third number    "; 
    cin >> num3; 

    // Compare numbers 1 and 2 for the largest number 
    if (num1 > num2) 
    { 
     largest = num1; 
    } 
    else 
    { 
     largest = num2; 
    } 

    // Compare largest to last number input 
    if (num3 > largest) 
    { 
     largest = num3; 
    } 

    // Display the largest number 
    cout << "largest number is: " << largest << endl; 

    // Increment the count 
    count++; 

    // Prompt user for the first number or to quit 
    cout << "If you want to quit enter " << SENTINEL << " to stop\n " << endl; 
    cout << "Enter first number "; 
    cin >> num1; 
} 

if (count > 0) 
{ 
    average = sum/count; 
    cout << "Average of the numbers is " << average; 
} 

return 0; 

注：我這裏沒有解決代碼錯誤，如在評論中提到的（變量沒有被宣佈，合計不被更新，等等）。