如何在 for 循环中使用开关盒？答案

【问题标题】：How to use a switch case inside a for loop?如何在 for 循环中使用开关盒？
【发布时间】：2022-01-02 15:03:11
【问题描述】：

我正在用 C++ 编程语言做一个测验程序。我使用了一个 for 循环来遍历每个 switch case，但是当我运行程序时，它只是不断循环 case 0 并且在我回答完我的测验后无法停止循环。我该如何解决？

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

void quiz_count () ;
void display_question () ;
void question (string question , string a , string b , string c , string d , char correct_answer) ;
void result () ;

int question_num = 0 ;
int correct = 0 ;
int wrong = 0 ;


int main ()
{
    display_question() ;
    return 0 ;
}

void quiz_count ()
{
    system("cls") ;
    cout << "Question Number: " << question_num << "\t\t Correct Answer:" << correct << "\t\t Wrong Answer:" << wrong << endl << endl ;
    display_question () ;
}

void display_question()
{
    for (int i=0; i<10 ; i++)
    {
        switch (i)
        {
            case 0 :
                question ( "1) What is recycling?" , "Buying new clothes" , "Collecting and using materials to make something new" , "Throwing things in garbage can" , "Selling items" , 'b' ) ;
                break ;
            case 1 :
                question ( "2) What are the 3R's of the recycling?" , "Redirect, Rude, Round" , "Respectful, Responsible, Right" , "Reduce, Reuse, Recycle" , "Rewrite, Rewind, Respond" , 'c') ;
                break ;
            case 2 :
                question ( "3) What goes into the green bin?" , "plastic" , "glass" , "cans" , "paper" , 'b' ) ;
                break ;
        }
    }
    result () ; 
}

void result ()
{
    system("cls") ; 
    cout << "The total of question is :" << question_num << endl ;
    cout << "The correct answer from you is :" << correct << endl ;
    cout << "The wrong answer from you is :" << wrong << endl ; 
}

void question (string question , string a , string b , string c , string d , char correct_answer)
{
    cout << question << endl ;
    cout << "A. \t" << a << endl ;
    cout << "B. \t" << b << endl ;
    cout << "C. \t" << c << endl ;
    cout << "D. \t" << d << endl ;
    char answer ;
    cout << "Please enter your answer here :" ;
    cin>>answer ;
    if (answer == correct_answer)
    {
        correct ++;
    }
    else 
        wrong ++ ;
    question_num ++ ;
    quiz_count() ;
}

【问题讨论】：

您会很高兴听到您不需要任何人的帮助来解决这个问题，只需一个您已经拥有的工具：您的调试器！这正是调试器的用途。 runs your program, one line at a time, and shows you what's happening，这是每个 C++ 开发人员都必须知道的事情。在调试器的帮助下，您将能够快速找到此程序以及您编写的所有未来程序中的所有问题，而无需向任何人寻求帮助。您是否已经尝试过使用调试器？如果不是，为什么不呢？您的调试器向您展示了什么？
display_question 递归调用自身：display_question 调用 question 调用 quiz_count 调用 display_question。对display_question 的每个嵌套调用都会重新开始循环。最有可能的是，您只想放弃来自quiz_count 的display_question 呼叫

标签： c++ loops for-loop switch-statement case

【解决方案1】：

问题不在于循环 + switch，而是您使用的无限递归：

display_question() 致电question()
question() 致电quiz_count()
quiz_count() 调用 display_question()，所以你回到了第 1 步。

您观察到的i 的值只是对display_question 函数的不同调用的值。

通过从quiz_count 中删除display_question() 调用，您可能会得到想要的结果。但是循环和switch 的组合在这里不是一个好的选择。除了更容易理解之外，以下实现产生了相同的结果：

void display_question()
{
    question ( "1) What is recycling?" , "Buying new clothes" , "Collecting and using materials to make something new" , "Throwing things in garbage can" , "Selling items" , 'b' ) ;
    question ( "2) What are the 3R's of the recycling?" , "Redirect, Rude, Round" , "Respectful, Responsible, Right" , "Reduce, Reuse, Recycle" , "Rewrite, Rewind, Respond" , 'c') ;
    question ( "3) What goes into the green bin?" , "plastic" , "glass" , "cans" , "paper" , 'b' ) ;

    result () ; 
}

【讨论】：