为什么我的输出显示计算器中的每个选项？ 我正在用C++（VisualStudio）做一个计算器，让你选择你想要的操作（加法、减法、乘法和除法），然后输入两个数字并得到答案。但是当我运行程序，在四个选项中选择并输入两个数字时，程序会显示每个选项的答案。这是代码，请告诉我我做错了什么，我应该做什么来显示我所做选择的答案 #include <iostream> using namespace std; int main() { int Q1Number, Num1, Num2, Answer; cout << "Welcome!" << endl; cout << "" << endl; cout << "Write the number to begin:" << endl; cout << " 1- Addition " << endl; cout << " 2- Subtraction " << endl; cout << " 3- Multiplication " << endl; cout << " 4- Division " << endl; cin >> Q1Number; cout << "Enter The first number"; cin >> Num1; cout << "Enter The second number"; cin >> Num2; if (Q1Number = 1) Answer = Num1 + Num2; cout << " Answer is : " << Answer << endl; if (Q1Number = 2); Answer = Num1 - Num2; cout << " Answer is : " << Answer << endl; if (Q1Number = 2); Answer = Num1 * Num2; cout << " Answer is : " << Answer << endl; if (Q1Number = 2); Answer = Num1 / Num2; cout << " Answer is : " << Answer << endl; } #包括 使用名称空间std； int main（） { 整数Q1，Num1，Num2，答案； cout

问题在于您的

if

语句。您需要使用

=

而不是

=

。使用

=

，您正在赋值，这就是问题所在

所以，改变

if (Q1Number = 1)

到

然后对所有

if

语句进行相同的编辑

---

当它是

=

时，运算符返回它指定的值，因此在您的情况下，指定的值是1和2，这将导致

为true

，因此满足

if

语句中的条件。

您实际上是在指定而不是测试（运算符=与运算符==不同）您应该在

if

语句中将

=

转换为

=

。
此外，如果要进行除法，则应选中

Num2！=0

#include <iostream>
using namespace std;

int main()
{

int Q1Number, Num1, Num2;
int Answer = 0;
cout << "Welcome!" << endl;
cout << "" << endl;
cout << "Write the number to begin:" << endl;
cout << " 1- Addition " << endl;
cout << " 2- Subtraction " << endl;
cout << " 3- Multiplication " << endl;
cout << " 4- Division " << endl;
cin >> Q1Number;
cout << "Enter The first number";
cin >> Num1;
cout << "Enter The second number";
cin >> Num2;
if (Num2 == 0 && Q1Number == 4)
    {
        cout << "Num2 is 0. We don't divide by zero" << endl;
        return 0;
    }

if (Q1Number == 1)
{
    Answer = Num1 + Num2;

    cout << " Answer is : " << Answer << endl;
}

if (Q1Number == 2)
{
    Answer = Num1 - Num2;

    cout << " Answer is : " << Answer << endl;
}

if (Q1Number == 3)
{
    Answer = Num1 * Num2;

    cout << " Answer is : " << Answer << endl;  
}

if (Q1Number == 4)
{
    Answer = Num1 / Num2;

    cout << " Answer is : " << Answer << endl;
}
return 0;

---

if（a=b）

意味着将

b

赋值给

a

，然后测试结果是否为

true

。每当

b

非零时，情况就是这样。要测试是否相等，需要使用

=

运算符，

if（a==b）

最好是将

cout
#include <iostream>
using namespace std;

int main()
{

int Q1Number, Num1, Num2;
int Answer = 0;
cout << "Welcome!" << endl;
cout << "" << endl;
cout << "Write the number to begin:" << endl;
cout << " 1- Addition " << endl;
cout << " 2- Subtraction " << endl;
cout << " 3- Multiplication " << endl;
cout << " 4- Division " << endl;
cin >> Q1Number;
cout << "Enter The first number";
cin >> Num1;
cout << "Enter The second number";
cin >> Num2;
if (Num2 == 0 && Q1Number == 4)
    {
        cout << "Num2 is 0. We don't divide by zero" << endl;
        return 0;
    }

if (Q1Number == 1)
{
    Answer = Num1 + Num2;

    cout << " Answer is : " << Answer << endl;
}

if (Q1Number == 2)
{
    Answer = Num1 - Num2;

    cout << " Answer is : " << Answer << endl;
}

if (Q1Number == 3)
{
    Answer = Num1 * Num2;

    cout << " Answer is : " << Answer << endl;  
}

if (Q1Number == 4)
{
    Answer = Num1 / Num2;

    cout << " Answer is : " << Answer << endl;
}
return 0;

 #include <iostream>
    using namespace std;

    int main()
    {

    int Q1Number, Num1, Num2, Answer;
    cout << "Welcome!" << endl;
    cout << "" << endl;
    cout << "Write the number to begin:" << endl;
    cout << " 1- Addition " << endl;
    cout << " 2- Subtraction " << endl;
    cout << " 3- Multiplication " << endl;
    cout << " 4- Division " << endl;
    cin >> Q1Number;
    cout << "Enter The first number";
    cin >> Num1;
    cout << "Enter The second number";
    cin >> Num2;

    if (Num2 == 0 && Q1Number == 4)
    {
        cout << "Num2 is 0. We don't divide by zero" << endl;
        return 0;
    }
    switch(Q1Number)
    {
        case 1:
            Answer = Num1 + Num2;
            break;
        case 2:
            Answer = Num1 - Num2;
            break;
        case 3:
            Answer = Num1*Num2;
            break;
        case 4:
            Answer = Num1/Num2;
            break;
        default: 
            cout << " Wrong option selected " << endl
            break;
    }

    cout << " Answer is : " << Answer << endl

    return 0;
}