请考虑以下代码：
string GameExit;
bool GameChoiceGo = true;
while (GameChoiceGo == true)
{
system("cls");
cout << "n Are you sure you want to exit? (Yes or No) ";
cin >> GameExit;
if (GameExit == "y" || "Y" || "yes" || "Yes" || "YES")
{
cout << "User typed Yes";
Sleep(3000);
system("cls");
break;
}
if (GameExit == "n" || "N" || "no" || "No" || "NO")
{
cout << "User typed No";
Sleep(3000);
system("cls");
GameChoiceGo = false;
}
else
{
cout << "nI'm sorry but, " << GameExit << " is not a acceptable choice. Type: Yes or No.nnn";
Sleep(3000);
system("cls");
}
}
break;
在这里，仅激活第一个语句。即使用户键入"No"或其他任何内容，它也会输出"user typed yes"。
如果我只用一个语句替换or statements，则else-if statements工作(即"y"和"n")。唯一的问题是，我希望用户可能在代码中输入任何可能的"是"和"否"版本。
知道为什么代码无法正常工作的任何想法？
很抱歉，但您必须为要检查的每个条件编写GameExit ==：
if (GameExit == "y" || GameExit == "Y" || GameExit == "yes" || GameExit == "Yes" || GameExit == "YES")
如果你写if ("y")(这基本上就是你正在做的事情，只是有更多的语句)，const char[]将衰减为const char*，并且该指针将与0进行比较。现在，该指针永远不会为 null，因为始终会为字符串文本分配内存。
更好的解决方案是 (1) 创建一个包含所有选项的数组，以便检查条件成为简单的搜索或 (2) 例如将输入转换为全部小写，并进行比较。
// 1)
std::vector<std::string> options = { "y", "Y", "yes", "Yes", "YES" };
if (std::find(options.begin(), options.end(), GameExit) != options.end());
// or
if (std::any_of(options.begin(), options.end(), [&GameExit](const auto& value) {
return GameExit == value;
});
// 2)
std::transform(GameExit.begin(), GameExit.end(), GameExit.begin(), ::tolower);
if (GameExit == "y" || GameExit == "yes");
如果您不知道函数:)做什么，可以查找它们。
在"your"代码中使用OR运算符的正确方法如下(请注意||运算符之间显式使用==语句)：
if (GameExit == "y" || GameExit =="Y" || GameExit =="yes" || GameExit =="Yes" || GameExit =="YES")
{
cout << "User typed Yes";
Sleep(3000);
system("cls");
break;
}
if (GameExit == "n" || GameExit =="N" || GameExit =="no" || GameExit =="No" || GameExit =="NO")
{
cout << "User typed No";
Sleep(3000);
system("cls");
GameChoiceGo = false;
}
PS：上面的答案并不是为了给出类似情况下的最佳编程实践，而是用最少的代码更改给出OP的具体答案:)
// -----
编辑：这是使用STL的更好方法。请注意，(未排序的)数组查找需要线性搜索，而unordered_set是一个哈希集，具有(平均)恒定时间查找。这将更快，特别是当是，否等选项很多时。
#include <unordered_set>
...
// These sets can be as large as possible or even dynamically
// updated while the program is running. insert, remove, lookup will
// all be much faster than a simple array.
unordered_set<string> ySet{"y", "Y", "yes", "Yes", "YES"};
unordered_set<string> nSet{"n", "N", "no", "No", "NO"};
if (ySet.find(GameExit) != ySet.end())
{
cout << "User typed Yes";
Sleep(3000);
system("cls");
break;
}
if (nSet.find(GameExit) != nSet.end())
{
cout << "User typed No";
Sleep(3000);
system("cls");
GameChoiceGo = false;
}
...
您需要为每个表达式定义一个完全相等，如下所示：
if ( gameExit == "y" || gameExit == "Y" ) {}
GameExit == "y" || "Y" || ....
是不正确的。正确的方法是：
GameExit == "y" || GameExit == "Y" || ....
等等，无论是"是"还是"否"情况。