C++中字符串条件判断语句失效问题求助

问题根源 #

你的代码中if和else if的条件判断写法错误，导致第一个分支永远被执行。

在C++中，逻辑或运算符||要求两侧都是布尔表达式。你写的answer == "yes" || "yeah"里，"yeah"是一个非空字符串字面量，会被隐式转换为布尔值true。这意味着整个条件answer == "yes" || true永远为真，不管answer输入什么，都会进入第一个分支输出Thats great!。

修正方法 #

对每个逻辑或的分支，都要完整写出变量与目标值的比较：

• 将if (answer == "yes" || "yeah")改为if (answer == "yes" || answer == "yeah")
• 将else if (answer == "no" || "nah")改为else if (answer == "no" || answer == "nah")

修正后的完整代码 #

#include <iostream>
#include <string>
using namespace std;
int main()
{
    std::string answer;

    cout << "Hello!" << '\n';
    cout << "Do you have a dog?" << endl;
    cin >> answer;
    if (answer == "yes" || answer == "yeah")
    {
        cout << "Thats great!";
    }
    else if (answer == "no" || answer == "nah")
    {
        cout << "Aww, thats too bad...";
    }
    else
    {
        cout << "Umm, I didn't get that." << '\n';
        cout << "Could you repeat that again?" << endl;
    }
    return 0;
}

内容的提问来源于stack exchange，提问作者Yashka