带有计数的 for 和 while 循环中的 C++ 哨兵。陷入无限循环

Question

我一直陷入代码的无限循环中。我必须做到这一点，这样您就可以使用哨兵“​​q”退出，但迭代次数不得超过 20 次。任何帮助将不胜感激，因为我只是编程新手。

#include <iostream>

using namespace std;

int main()
{
    int option; // If new member or existing member or exit
    char SENTINEL = 'q';
while(option != SENTINEL)
{
    for(int count = 0; count <= 20; count++)
    {   
        // Display menu
        cout << "Welcome to the forum.\n";
        cout << "Are you:\n";
        cout << "1. A new member\n";
        cout << "2. An existing member" << endl;
        cout << "To exit press 'q'\n";
        cin >> option;

        if (option == 1)
        {
            char new_name[20]; // Array to hold new member 

            cout << "You're a new member.\n"; 
            cout << "Please enter your first name followed ";
            cout << "by your last name.\n";
            cout << "Then press return.\n";

            cin >> new_name; // User enter their name
        }
        else if (option == 2)
        {
            cout << "You're an existing member." << endl;
        }
    } 
}
}

Answer 1

您需要执行以下操作:

1. 摆脱 while 循环。您需要使用一个具有多个条件的循环，或者在循环内从它break。
2. 将 option 设为 char 而不是 int。将 option 与 SENTINEL 进行比较没有意义，因为它们是不同的类型。将 option 设为 char 将解决此问题。
3. 使用 string 类而不是包含 20 个元素的 char 数组。名字和姓氏超过 20 个字符的任何人都会导致缓冲区溢出。 string 更安全，如果需要会自动扩展。

---

#include <iostream>
#include <string>

using namespace std;

int main()
{
    char option; // If new member or existing member or exit
    char SENTINEL = 'q';

    for(int count = 0; count <= 20; count++)
    {   
        // Display menu
        cout << "Welcome to the forum.\n";
        cout << "Are you:\n";
        cout << "1. A new member\n";
        cout << "2. An existing member" << endl;
        cout << "To exit press 'q'\n";
        cin >> option;
        cin.get(); // discard newline char

        if (option == '1')
        {
            string new_name; // string to hold new member 

            cout << "You're a new member.\n"; 
            cout << "Please enter your first name followed ";
            cout << "by your last name.\n";
            cout << "Then press return.\n";

            getline(cin, new_name); // User enter their name
        }
        else if (option == '2')
        {
            cout << "You're an existing member." << endl;
        }
        else if (option == SENTINEL) {
            break; // break from the loop
        }
    } 
}