CODEWITHSUNDEEP
c++arraysloopsfor-loopwhile-loop
Connor Lance
Connor Lance

Reputation: 77

Array not initializing properly within a while loop

My issue is that I have set up an array to store totals that were calculated from values read from a file. These stored totals are then added together to find the over all average.

This issue is stemming from a 'cin' at the beginning of the program where the user inputs a number and that number is supposed to drive the program by setting how many times the program loops and how many modules are inside the array. The array does not seem to work properly no matter how much I try.

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>

using namespace std;

int main()
{
    string StudentGrades;
    int studentID;
    double quiz1;
    double quiz2;
    double quiz3;
    double quiz4;
int total = 0;
double choice;
ofstream outFile;
double numStud=1;

cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
outFile.open("StudentGrades.txt");
cout << "How many students would you like to enter?" << endl;
cin >> numStud;

for (int x = 0; x < numStud; x++)
{
    cout << "Enter student ID: ";
    cin >> studentID;
    cout << "Enter quiz grade 1: ";
    cin >> quiz1;
    //cout << quiz1;
    cout << "Enter quiz grade 2: ";
    cin >> quiz2;
    //cout << quiz2;
    cout << "Enter quiz grade 3: ";
    cin >> quiz3;
    //cout << quiz3;
    cout << "Enter quiz grade 4: ";
    cin >> quiz4;
    //cout << quiz4;
    cout << endl;
    //outFile.open("StudentGrades.txt");
    if (outFile.is_open())
    {
        cout << "inside if/else outFile" << endl;
        //outFile << "File successfully open";

        outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;

    }
    else
    {
        cout << "Error opening file";
    }
    outFile.close();
    /*cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
    cin >> choice;
    if (choice == 1)
        continue;
    if (choice == 0)
    {
        outFile.close();
        break;
    }*/

}



ifstream inFile;
inFile.open("StudentGrades.txt");
int sTotal;
int total[numStud];
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
    //cout << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
    total = (quiz1 + quiz2 + quiz3 + quiz4);
    sTotal = total[numStud];

    double avg = total / 4;


}


system("pause");
return 0;

}

Upvotes: 1

Views: 67

Answers (1)

NathanOliver
NathanOliver

Reputation: 180965

int total[numStud]; is a variable length array and is not standard in C++. If you need an array and you don't know what the size will be then you should use a std::vector. A vector can be used almost exactly as an array can. For example you could would become:

int total;
std::vector<int> studentTotal;
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
    //cout << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
    studentTotal.push_back(quiz1 + quiz2 + quiz3 + quiz4); // insert into the vector at the end
    total += studentTotal.back();  // get last inserted element
}

Upvotes: 2

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