Nrthugu

The program requires the user to input numbers and when finished to exit the loop by entering a negative number. The program will then output the average of the numbers and the count of the numbers. The negative number should be removed from the series though. So if we have three numbers and exit on the (fourth) negative number, the average will only be of the three numbers and not include the negative number. Neat, I somehow made that work. Now, I need to expand upon this to make it so that the input is verified to be an integer and less than 100 also using a Boolean equation. It is at this point that I cannot determine how to exclude the erroneous input from the results.

#include <iostream>

#include <iomanip>



using namespace std;



int main ()

{

    float inScore= 1;

    float sumScore= 0.0;

    int scoreCount= 0;

    float avgScore= 0.0;

    bool moreNumbers = true;

    bool notNumbers = true;





    for ( inScore =1; inScore >=1; inScore++)  //for loop some kind of blackmagic not really sure about this right now

    {

        cout << "Please enter grades (enter a negative integer to exit): ";

        cin >> inScore;

        if (!cin || inScore > 100)

        {

            notNumbers = false;  //boolean to ignore non integers or numbers greater than 100

            cin.clear();

            cin.ignore(256, 'n');

            scoreCount--;

            cout << "Invalid number!" << endl;

        }         //something is wrong in this section and I can't get it to ignore the invalid inputs



        else if (inScore < 0)

        {

            moreNumbers = false;

        }         //breaks the loop upon a negative number being entered

        else

            sumScore+=inScore;

        scoreCount++;

    }

    avgScore = (sumScore+=inScore)/(scoreCount-1);

    cout << "Number of Grades: " << scoreCount-1 << endl;  //number of entries

    cout << "Average: " << avgScore << endl;                // average grade except I cannot figure out how to remove negative number from the array



    return 0;

}

Remaining Problem

Now, I need to expand upon this to make it so that the input is verified to be an integer and less than 100

Since the above current code accepts floating point values as valid inputs, we must fix the code and exclude them as invalid inputs.
For instance, if we input 1.5, 2.5 and -1, then these values are accepted and output

Number of Grades: 2

Average: 2

is shown.
Also, the current code accepts two or more integers from just one input.
If we give an input 1.5 2.5 -1, then the above output is again shown.
But we should judge 1.5, 2.5 and 1.5 2.5 -1 as invalid inputs!

Definition of the Valid Input

Since I don't know your precise definition of valid input and I may be wrong, but here I assume that it is given by the following natural statements.
First of all, as you say,

• Each input represents an integer.

Therefore, I assume

• Whitespace characters are allowed in the left and right side of input strings.




• Whitespace characters between non-whitespace characters are not allowed.

In addition, I also assume

• The first non-whitespace character must be 0, 1, ..., 9, + or -.




• The second and the subsequent non-whitespace characters must be 0, 1, ..., 8 or 9.

Note that in my assumption the decimal-point character . is not allowed.

For instance, " 123 ", " +123 " and " -123 " are all valid inputs. But " 1 23", "+ 123", "- 123", "1.0" and "123a" are all invalid.

Validity Check Function

First, to check the validity of the input, using the following nice trimming function, we trim the input string and remove left and right whitespaces:

std::string_view trimLR(std::string_view str)

{

    const auto strBegin = str.find_first_not_of(" fnrtv");

    if (strBegin == std::string_view::npos){

        return "";

    }



    const auto strEnd = str.find_last_not_of(" fnrtv");

    const auto strRange = strEnd - strBegin + 1;



    return str.substr(strBegin, strRange);

}

Next, we define the following simple validity check function isInteger which checks whether the passed string is an integer or not.
Here std::isdigit is useful to check each character is one of the 10 decimal digits: 0, 1, ..., 9.

My DEMO is here.

bool isInteger(std::string_view s)

{

    s = trimLR(s);



    if(s.empty()){

        return false;

    }



    const std::size_t offset = ((s[0] == '-') || (s[0] == '+')) ? 1 : 0;

    const auto begin = s.cbegin() + offset;





    return (begin != s.cend()) // remove "+" and "-"

             && std::all_of(begin, s.cend(), (unsigned char c){             

                  return std::isdigit(c);

                });

}

In addition to this method, various interesting methods are proposed in past posts.

Main Function

Now it is easy and straightforward to implement the main for-loop.
The following code will work fine.
The input is verified to be an integer and less than 100.

int main()

{

    double sumScore = 0;

    int scoreCount  = 0;



    for(;;)

    {

        std::string s;

        std::cout << "Please enter grades (enter a negative integer to exit): ";

        std::getline(std::cin, s);



        if(!isInteger(s)) {

            std::cout << "Invalid number!" << std::endl;

            continue;

        }



        const auto score = std::stoi(s);

        if(score < 0) {

            std::cout << "Negative number is input, Finished!" << std::endl;

            break;

        }

        else if(score > 100) {

            std::cout << "Input value is grater than 100, which is ignored." << std::endl;

            continue;

        }



        sumScore += score;

        ++scoreCount;

    }



    const auto average = (scoreCount == 0) ? 0 : (sumScore/scoreCount);



    std::cout

        << "Number of Grades: " << scoreCount << std::endl

        << "Average: " << average << std::endl;



    return 0;

}