或不等于

本文介绍了或不等于的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

这为什么起作用?

#include <iostream> #include <string> using namespace std; int main(){ string s="a"; if((s=="cm")||(s=="in")||(s=="ft")||(s=="m")) cout<<s+" Is an illegal value"; else cout<<"I like "+s; return 0; }

ideone/7pnYh

但是那不是

#include <iostream> #include <string> using namespace std; int main(){ string s="a"; if((s!="cm")||(s!="in")||(s!="ft")||(s!="m")) cout<<s+" Is an illegal value"; else cout<<"I like "+s; return 0; }

ideone/TXUXA 我想要的答案都是我喜欢".

ideone/TXUXA The answer i want for both is "I like a" .

推荐答案

在第二种情况下， s！="cm" ，当然还有第一个 cout .要取消检查并保持逻辑不变，请执行以下操作:

In your second case s != "cm" and of course the first cout is printed. To negate the check and the logic to remain the same, do it like this:

if((s!="cm")&&(s!="in")&&(s!="ft")&&(s!="m")) cout<<"I like "+s; else cout<<s+" Is an illegal value";