c++ - 如何使用 else if 语句来比较字母并使其不区分大小写？

Question

所以我这里有这段代码:

string answer1;

answerQues1:    
    cout << "So, A, B, C or D?";
    cin >> answer1;

     if (answer1 == "A" | answer1 == "a")
        {
            cout << "It's the right answer, you have " << char(156) << "100!" << endl;
            PlaySound(TEXT("C:/Users/user/Downloads/Millionaire/£100correct.wav"), NULL, SND_FILENAME | SND_ASYNC );
            Sleep(2000);
        }

    else if (answer1 >= "E" | answer1 >= "e") //FIX THIS, IT'S ONLY ACCEPTING CAPITALS NOT LOWERCASES.
        {
            cout << "Whoops, you've entered an incorrect option! Remember, only A, B, C or D are acceptable." << endl;
            answer1.erase();
            goto answerQues1;
        }    

     else
        {
            cout << "I'm very sorry, it's an early exit for you - it's the wrong answer! You leave with nothing!" << endl;
            PlaySound(TEXT("C:/Users/user/Downloads/Millionaire/£100and£64000lose.wav"), NULL, SND_FILENAME | SND_ASYNC);
            Sleep (4000);
            PlaySound(TEXT("C:/Users/user/Downloads/Millionaire/gameOver.wav"), NULL, SND_FILENAME | SND_ASYNC);
            cout << "Thanks for playing! Press any key to exit the game" << endl;
            system("pause");
            return 0;
        }

else if 语句检查答案是否大于或等于字母 E，因为只有 A、B、C 或 D 是可接受的。然后它显示一条消息告诉用户，删除 answer1 的值，然后返回到输入部分，本质上是一个循环。但是，当我输入一个不正确的选项(例如 E)并立即输入一个可接受的选项(例如 B)时，它不会接受 B 作为错误答案，而是不会转到 else 语句，而是转到 else if ONLY IF THE ANSWER IS LOWERCASE .但是如果我用大写字母输入 B，它会认为它是错误的，并按照它应该的方式转到 else 语句。无论如何我可以解决这个问题以便它检测大写和小写字母吗？非常感谢。

Answer 1

问题是小写字母大于大写字母。请参阅 ASCII 表:http://www.asciitable.com/ .你可能想要:

else if ((answer1 >= "E" && answer1 <= "Z") || answer1 >= "e")