I don't know what is wrong with this array builder

closed account (9hv4jE8b)
I'm trying to write a function that will build an array for me. But I know it doesnt work because when I print part of the array it comes out with a large (9 digit?) number.

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int collect_data(int grades[][8], int Num_of_Students) //a nested for loop that builds a 2-D array
{   int j; //counter for which project it is
    int i; //counter for which student
    int grade;
    
    for(j=0;j<8;j++){
        for(i=0;i<Num_of_Students;i++){
            cout << "Please give grade of student " << i+1 <<  " in project " <<j+1 << ": ";
            cin >> grade;
            grade=grades[i][j];
            }
    } 
    return grades[i][j];
}

This is my first time working with 2-d arrays, so I think that is the problem. I'm also not sure if I'm passing it to my main correctly.

Thanks guys.
budman85 (34)

Reverse the assignment in line 10.

grades[i][j] = grade;

Since you are passing the array grades by reference,
you will be updating the array directly.

So no need to return any value (last students project #8 grade).
You could remove line 13 and change the returning int to void in line 1.

void collect_data (int grades[][8], int Num_of_Students)

And you should be all set.






Last edited on
closed account (9hv4jE8b)
Oh ok, I see what you did.

I'm still not sure if mine is working properly though. Here's my tentative main where I'm trying to see grades[0][0];
Skip down to line 42 where I try to cout. It doesnt print anything, so I'm a bit confused.

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#include<iostream>
#include<cmath>

using namespace std;

void collect_data (int grades[][8], int Num_of_Students); //Gets data to store in array
float compute_ave(int grades[][8], int Num_of_Students); //Prototype for computing the average of a specific exam
float class_average(int grades[][8], int Num_of_Students);


int main()
{
     
     cout << "Student Exam Database\nThis program stores the exam scores\n";
     cout << "of a number of students and produces\nthe average and the letter grades." << endl << endl;

     int choice; //for picking option
     int flag=0; //because you must input data first
     int Num_of_Students; //Number of students in class
     int grade;
     int grades[][8]={}; //the empty array
              
     do{ 
         cout << "Please choose an option." << endl;
         cout << "1. To store students exams." << endl;
         cout << "2. To compute class average on a specific exam." << endl;
         cout << "3. To compute overall class average in the course." << endl;
         cout << "4. To see the letter grade of a specific student." << endl;
         cout << "Please choose: ";
         cin >> choice;
             if (choice==1 && flag==0){
                cout << "Please give number of students: " <<endl;
                cin >> Num_of_Students;
                collect_data(grades, Num_of_Students);
                     
                flag=1;}
                
             else if(choice==2 && flag==0){
                  cout << "No scores stored yet." <<endl;
                  }
             else if(choice==2 && flag==1){
                  cout << grades[0][0];
                  }
             else if(choice==3 && flag==0){
                  cout << "No scores stored yet." <<endl;
                  }
             else if(choice==3 && flag==1){
                  
                  }
         
                              
          }while(choice!=0);


system("pause");

}


void collect_data (int grades[][8], int Num_of_Students) //a nested for loop that builds a 2-D array
{   int j; //counter for which project it is
    int i; //counter for which student
    int grade;
    
    for(j=0;j<8;j++){
        for(i=0;i<Num_of_Students;i++){
            cout << "Please give grade of student " << i+1 <<  " in project " <<j+1 << ": ";
            cin >> grade;
            grades[i][j]=grade;
            }
    } 

}
closed account (9hv4jE8b)
nvm it's working
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