Question

嘿，有人可以伸出援助之手吗？如何在第一次计算后使循环结束？在我完成一个计算，如加法后，我想结束它。对不起noobie问题。我现在正在课堂上学习循环。非常感谢。

#include <iostream>
#include <string>

using namespace std;

int main()
{
    int numOne;
    int numTwo;
    int result;
    string operation;

    cout << "Please enter what operation you'd like to perform or e/E to end program: ";
    cin >> operation;
    while (operation == "e" || operation == "E")
    {
        cout << "Operation type invalid." << endl;
        cout << "Please enter what operation you'd like to perform or e/E to end program: ";
        cin >> operation;
    }

    while (operation == "+" || operation == "-" || operation == "*" || operation == "/")
    {
        cout << "Please enter integer one: ";
        cin >> numOne;
        cout << "Please enter integer two: ";
        cin >> numTwo;

    if (operation == "+")
    {
        result = numOne + numTwo;
        cout << "The numbers you entered were " << numOne << "," << numTwo << endl;
        cout << "The operation you chose was " << operation << "." << endl;
        cout << "The operations result is " << result << "." << endl;
        cout << "Your equation was: " << numOne << " " << operation << " " << numTwo << " = " << result << ".";
    }
    else if (operation == "-")
    {
        result = numOne - numTwo;
        cout << "The numbers you entered were " << numOne << "," << numTwo << endl;
        cout << "The operation you chose was " << operation << "." << endl;
        cout << "The operations result is " << result << "." << endl;
        cout << "Your equation was: " << numOne << " " << operation << " " << numTwo << " = " << result << ".";
    }
    else if (operation == "*")
    {
        result = numOne * numTwo;
        cout << "The numbers you entered were " << numOne << "," << numTwo << endl;
        cout << "The operation you chose was " << operation << "." << endl;
        cout << "The operations result is " << result << endl;
        cout << "Your equation was: " << numOne << " " << operation << " " << numTwo << " = " << result << ".";
    }
    else if (operation == "/")
    {
        if (numTwo == 0)
        {
                cout << "You cannot divide by zero!" << endl;
        }
        else
        {
        result = numOne / numTwo;
        cout << "The numbers you entered were " << numOne << "," << numTwo << endl;
        cout << "The operation you chose was " << operation << "." << endl;
        cout << "The operations result is " << result << endl;
        cout << "Your equation was: " << numOne << " " << operation << " " << numTwo << " = " << result << ".";
        }
    }

    }
    return 0;
}

我不允许使用break。还有另一种方式吗？

Answer 1

只需将while更改为if即可。如果你只想执行一次，就不需要循环。

Answer 2

我对C ++不是很熟悉，但我认为你的意思是break;语句

https://msdn.microsoft.com/library/37zc9d2w.aspx

Answer 3

使用

break;

这将每次结束循环。您可以在其周围包装if语句以应用退出条件。

Answer 4

代码块：

cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
while (operation == "e" || operation == "E")
{
    cout << "Operation type invalid." << endl;
    cout << "Please enter what operation you'd like to perform or e/E to end program: ";
    cin >> operation;
}

不做你所承诺的用户：

Please enter what operation you'd like to perform or e/E to end program:

如果输入"e"或"E"，循环将不会停止并再次请求输入。

你可能想要这样的东西：

do {
    cin >> operation;
    while (operation == "+" || operation == "-" || operation == "*" || operation == "/") {
        // ...
   }
} while(operation != "e" && operation != "E");

至于你愚蠢的限制，不要使用do {} while();（踢你的教授，至少做两次）：

cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
while(operation != "e" && operation != "E") {
    if (operation == "+" || operation == "-" || operation == "*" || operation == "/") {
        // ...
    }
    else {
        cout << "Operation type invalid." << endl;
        cout << "Please enter what operation you'd like to perform or e/E to end program: ";
        cin >> operation;
    }
}

Answer 5

如果你必须使用while循环，只需添加break;这将打破循环。如果您不必，我会将其更改为if语句。示例：if（varName =='+'）{

Num1 + num2;}

对不起格式化，在手机上

Answer 6

我想你实际上想要实现的是这个。第一个循环应该重构（即：循环直到操作为'e'或'E'），第二个循环应该是if-else语句（检查操作是否有效）。

int main()
{
    int numOne;
    int numTwo;
    int result;
    string operation;

    cout << "Please enter what operation you'd like to perform or e/E to end program: ";
    cin >> operation;
    while (operation != "e" && operation != "E") {

        if (operation == "+" || operation == "-" || operation == "*" || operation == "/") {
             // your valid operation code...
        } else {
            cout << "Operation type invalid." << endl;
        }

        cout << "Please enter what operation you'd like to perform or e/E to end program: ";
        cin >> operation;
    }

    return 0;
}

如何结束我的while循环？

6 个答案: