c++ - 为什么我的 switch case 被跳过并打印 default ？

Question

我编写此 C++ 代码是为了模拟自动售货机。每当输入用户的选择时，数字 1-5 在 switch 语句中各分配一个 case，所有 case 都不会执行:程序无法识别有效输入，只会打印出 default case 语句。为什么会这样？

#include <iostream>

using namespace std;

int main()
{
    int choice;
    double dollars;

    cout << "==============================================================\n";
    cout << "*                                                            *\n";
    cout << "*              VENDING MACHINE SIMULATOR                     *\n";
    cout << "*                                                            *\n";
    cout << "==============================================================\n";

    cout << "Your Choices Are:\n";

    cout << "1) Coke     - $1.75\n";
    cout << "2) Pepsi    - $2.25\n";
    cout << "3) Sprite   - $1.25\n";
    cout << "4) 7-up     - $1.15\n";
    cout << "5) Water    - $2.20\n";

    // Ask for user's selection.

    cout << "What would you like to purchase today?\n";
    cin >> choice;
    switch (choice)
    {
            case '1': 
            {
                    cout << "How many dollar bills will you use?\n";
                    cin >> dollars;
                    {
                            if (dollars > 1.75)
                            {
                                    cout << "You purchased: Coke\n";
                                    cout << "Your change is: $"<< (dollars - 1.75);
                            }
                            else
                            {
                                    cout << "You do not have enough money for this purchase. Goodbye!\n";
                            }
                    }
            }
                      break;
            case '2':
            {
                    cout << "How many dollar bills will you use?\n";
                    cin >> dollars;
                    {
                            if (dollars > 2.25)
                            {
                                    cout << "You purchased: Pepsi\n";
                                    cout << "Your change is: $"<< (dollars - 1.75);
                            }
                            else
                            {
                                    cout << "You do not have enough money for this purchase. Goodbye!\n";
                            }
                    }
            }
            case '3': 
            {
                    cout << "How many dollar bills will you use?\n";
                    cin >> dollars;
                    {
                            if (dollars > 1.25)
                            {
                                    cout << "You purchased: Sprite\n";
                                    cout << "Your change is: $"<< (dollars - 1.25);
                            }
                            else
                            {
                                    cout << "You do not have enough money for this purchase. Goodbye!\n";
                            }
                    }
            }
                      break;
            case '4': 
            {
                    cout << "How many dollar bills will you use?\n";
                    cin >> dollars;
                    {
                            if (dollars > 1.15)
                            {
                                    cout << "You purchased: 7-up\n";
                                    cout << "Your change is: $"<< (dollars - 1.15);
                            }
                            else
                            {
                                    cout << "You do not have enough money for this purchase. Goodbye!\n";
                            }
                    }
            }
                      break;
            case '5': 
            {
                    cout << "How many dollar bills will you use?\n";
                    cin >> dollars;
                    {
                            if (dollars > 2.20)
                            {
                                    cout << "You purchased: Water\n";
                                    cout << "Your change is: $"<< (dollars - 2.20);
                            }
                            else
                            {
                                    cout << "You do not have enough money for this purchase. Goodbye!\n";
                            }
                    }
            }

                      break;
            default: cout << "Your choice is INVALID. Goodbye!\n"; 
     }
    return 0;
}

Answer 1

删除 case 语句中使用的单引号。

改变

 case '1':

到

case 1: 

其他人也一样。

'1' 是字符常量，而 1 是整数常量。当使用 ASCII 编码时，'1' 的计算结果为数字 49，这显然不等于数字 1。因此，当您输入 1 作为输入时，case: 分支不会执行。