Question

我是C ++的新手，当我遇到打嗝时正在尝试这个程序。这不是技术问题。程序运行得很好。

#include<iostream>    
int main()
{
    using namespace std;
    int num1, num2;
    char ch;
    cout << "Enter the two integers: ";
    cin >> num1 >> num2;
    cout << "Choose one of the following arithmetic operators: " << endl;
    cout << "+" << endl;
    cout << "-" << endl;
    cout << "*" << endl;
    cout << "/" << endl;
    cin >> ch;
    if (ch == '+')
        cout << "The sum of the two numbers is: " << num1 + num2 << endl;
    if (ch == '-')
        cout << num2 << " subtracted from " << num1 << " is " << num1 - num2 << endl;
    if (ch == '*')
        cout << "When multiplied: " << num1*num2 << endl;
    if (ch == '/')
        cout << num1 << " divided by " << num2 << " will be " << num1 / num2 << endl;
    else
        cout << "Wrong input. Try again.";
    return 0;
}

现在问题就在于此。当满足if语句以及提供的计算时，输出还会显示else语句中的语句。我尝试将else编辑为： -

else if(ch=!'+','-','*','/')

和

if(ch=!'+','-','*','/')

但它们似乎都没有用。在所有情况下，“错误的输入。再试一次。”以某种方式找到输出的方式。我哪里错了？

Answer 1

您的整个结构必须是if - else if - else，如下所示：

if(ch=='+')
    cout<<"The sum of the two numbers is: "<<num1+num2<<endl;
else if(ch=='-')
    cout<<num2<<" subtracted from "<<num1<<" is "<<num1-num2<<endl;
else if(ch=='*')
    cout<<"When multiplied: "<<num1*num2<<endl;
else if(ch=='/')
    cout<<num1<<" divided by "<<num2<<" will be "<<num1/num2<<endl;
else 
    cout<<"Wrong input. Try again.";

但这是最好的做事方式吗？可能不是。既然您只是在测试以查看ch等于什么，那么您实际上可以使用另一个内置的C ++构造，即switch语句：

switch (ch) {
  case '+':
    cout << "The sum of the two numbers is: " << num1+num2 << endl;
    break;
  case '-':
    cout << num2 << " subtracted from " << num1 << " is " << num1-num2 << endl;
    break;
  case '*':
    cout << "When multiplied: " << num1*num2 << endl;
    break;
  case '/':
    cout << num1 << " divided by " << num2 << " will be " << num1/num2 << endl;
    break;
  default:
    cout << "Wrong input. Try again." << endl;
    break;
}

Answer 2

在原始代码中，PATH仅适用于最后一个PYTHONPATH语句。你需要链接你的条件：

else

但是，您最好使用if语句：

if(ch=='+')
    cout<<"The sum of the two numbers is: "<<num1+num2<<endl;
else if(ch=='-')
    cout<<num2<<" subtracted from "<<num1<<" is "<<num1-num2<<endl;
else if(ch=='*')
    cout<<"When multiplied: "<<num1*num2<<endl;
else if(ch=='/')
    cout<<num1<<" divided by "<<num2<<" will be "<<num1/num2<<endl;
else 
    cout<<"Wrong input. Try again.";

Answer 3

当else不等于ch时，

/部分将始终执行，因为else部分仅与if(ch=='/')匹配。可能您想使用if else阶梯或转换案例。

Answer 4

＆＃34; Else-statement＆＃34;与最后的＆＃34; if-statement＆＃34;相关联。因此，如果非最后一个if语句avaliates为true，那么最后一个将avaliate为false，这意味着对else语句的真实avaliation。您可以将if语句更改为＆＃34;否则，如果＆＃34; （不要使用第一个if语句）。

为什么'else'语句出现在输出中？

4 个答案: