Question

我必须编写一个用多个用户输入来计算GPA的程序。

如果输入正确，我已经得到了正确计算GPA的程序，但是，程序还必须进行错误检查，即如果用户在输入实际需要为0,1,2,3时输入5，或4.我需要能够告诉用户输入无效并让程序返回一步并允许它们重试。

程序无法使用数组。

#include <iostream>
using namespace std;
int main ()
{

//Defining variables that will be used during code.
float CreditHours;
int LetterGrade;
float Total;
float TotalCredits = 0;
float TotalPoints = 0;
//Asking for input from user
cout<<"Please enter the grade for your class: 4 for A, 3 for B, 2 for C, 1 for D, 0 for F,  or  '-1' when you're done inputting grades:\n";    

cin >> LetterGrade;
// Logic to ensure valid letter grade input
if ((LetterGrade >= 4) && (LetterGrade <= 0))
{
    cout << "Please enter a valid input (0, 1, 2, 3, or 4):\n";
    cin >> LetterGrade;
}

cout << "Please enter the credit hours for the previously entered grade: \n";

cin >> CreditHours;


//initializing the loop for more grade inputs
//FIX LOOP
while (LetterGrade != -1)
{

    //Updating Totals
    Total = LetterGrade * CreditHours;
    TotalPoints = TotalPoints +  Total;
    TotalCredits = TotalCredits + CreditHours;

    cout << "Please enter the grade for your class: 4 for A, 3 for B, 2 for  C, 1 for D, 0 for F, or -1 when you're done inputting grades:\n";

    cin >> LetterGrade;

    if (LetterGrade != -1)
    {
        cout << "Please enter the credit hours for the previously entered grade: \n";

        cin >> CreditHours;
    }
}//close loop
//Incomplete/Questionable

if (TotalCredits <= 0)
{
    cout << "Please be sure your Credit Hours add up to a positive, non-zero value\n";
}
else if (TotalCredits > 0)
{
    //Calculating and printing the final GPA.
    float gpa = TotalPoints / TotalCredits;

    cout << "Your GPA is:"<< gpa <<endl;
}
return 0;

Answer 1

您可以将if语句更改为while循环，以便在输入有效的数字/数据类型之前程序不会继续。您还可以使用isdigit（）来检查输入是否为数字。

Answer 2

你可以放一段时间：

#include <iostream>
using namespace std;
int main ()
{

//Defining variables that will be used during code.
float CreditHours;
int LetterGrade;
float Total;
float TotalCredits = 0;
float TotalPoints = 0;
//Asking for input from user
cout<<"Please enter the grade for your class: 4 for A, 3 for B, 2 for C, 1 for D, 0 for F,  or  '-    1'     when you're done inputting grades:\n";    

while (true)
{
    cin >> LetterGrade;
    if ((LetterGrade >= 4) && (LetterGrade <= 0))
       cout << "Please enter a valid input (0, 1, 2, 3, or 4):\n";
    else
        break;
}
cout << "Please enter the credit hours for the previously entered grade: \n";

cin >> CreditHours;

Answer 3

Guga00的答案似乎是正确的。另请注意，您应该更改条件以检查有效的信件。您目前正在检查 LetterGrade 是否大于4且小于0，这将永远不会成立。尝试使用以下内容：

if ((LetterGrade > 4) || (LetterGrade < -1))

我更改了＆amp;＆amp; （AND）for || （要么）。检查 LetterGrade 是否大于4或小于-1。如果输入无效，它将返回 true 。我添加了-1以允许您检测输入的结束。

如果在c ++中输入无效，如何重复输入命令

3 个答案: