Thread: From files to vectors and arrays.

>> does it involve another for loop with an i-- in it
That sounds like it could work.

alright, i did some more coding and changed the for loop to a while loop:

to store in the vectors and array:

Code:

int i=0;
while (!fileout.eof())
{
fileout >> ssn[i];
fileout.ignore(80,'\n');
getline (fileout,name[i]);
fileout >> gpa[i];
i++;
fileout >> ws;
}

to list them backwards: (excluding the setw, will add later)
will the set precision below only effect the gpa?

Code:

for (int j = i; j >=0; j--)
{
cout << ssn[j] << name[j] << setiosflags (ios::fixed | ios::showpoint) << setprecision(2) << gpa[j] << endl;
}

to find the average gpa:
but im confused, since it starts at 0, should i divide by i or (i+1)?

Code:

int tot = 0;
int aver;
for (int k = 0; k < i; k++)
{
tot += gpa [k];
aver= tot/i;
}

>> i did some more coding and changed the for loop to a while loop
That's fine, but now you have no check for going over the 35 maximum. I'm not sure if your assignment requires it, but if it does you should check i after incrementing and break the loop if it reaches 35.

>> will the set precision below only effect the gpa?
I would think so, since setprecision should not affect integer or string output.

>> since it starts at 0, should i divide by i or (i+1)?
The 0 start doesn't add anything to the sum, so it should not affect the average. You might consider doing the division after the loop, though, since it's useless to calculate that value over and over inside the loop.

I think this is right.... but i have errors:

Code:

aname9.cpp: In function `int main()':
aname9.cpp:43: warning: assignment to `int' from `double'
aname9.cpp:43: warning: argument to `int' from `double'







//Name
//Program 9
//Write a program that reads info from a dat file and stores it in vectors and arrays.

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

using namespace std;

int main ()
        {//int main open
                vector <string> name (35);
                ifstream fileout;
                vector <int> ssn (35) ;
                double gpa [35];
                fileout.open("students.dat");
                        if (fileout.fail())
                        {
                        cerr << "Unable to open file." << endl;
                        }
                int i=0;
                while (!fileout.eof())
                        {
                        fileout >> ssn[i];
                        fileout.ignore(80,'\n');
                        getline (fileout,name[i]);
                        fileout >> gpa[i];
                        i++;
                        fileout >> ws;
                        }
                for (int j = i; j >=0; j--)
                        {
                        cout << ssn[j] << setw(20) << name[j] << setw(10) << setiosflags (ios::fixed | ios::showpoint) << setprecision(2) << gpa[j] << endl;
                        }
                cout << endl;
                int tot = 0; 
                int aver;
                for (int k = 0; k < i; k++)
                        {
                        tot += gpa [k]; 
                        }
                aver= tot/i;
                cout << "Total number of students: " << i << endl;
                cout << "Average GPA: " << aver;
        return 0;
        }//int main close

getting there...

my output is just looking odd... new code:

Code:

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

using namespace std;

int main ()
        {//int main open
                vector <string> name (35);
                ifstream fileout;
                vector <int> ssn (35) ;
                double gpa [35];
                fileout.open("students.dat");
                        if (fileout.fail())
                        {
                        cerr << "Unable to open file." << endl;
                        }
                int i=0;
                while (!fileout.eof())
                        {
                        fileout >> ssn[i];
                        fileout.ignore(80,'\n');
                        getline (fileout,name[i]);
                        fileout >> gpa[i];
                        i++;
                        fileout >> ws;
                        }
                cout << setw(9) << "SS Number" << setw(20) << "Name" << setw(10) << "GPA" << endl;
                for (int j = i; j >=0; j--) 
                        {
                        cout << ssn[j] << setw(20) << name[j] << setw(10) << setiosflags (ios::fixed | ios::showpoint) << setprecision(2) << gpa[j] << endl;
                        }
                cout << endl;
                double tot = 0;
                double aver;
                for (int k = 0; k < i; k++)
                        {
                        tot += gpa [k];
                        }
                aver= tot/i; 
                cout << "Total number of students: " << i << endl;
                cout << "Average GPA: " << aver;  
        return 0;
        }//int main close

output:

Code:

SS Number                Name       GPA
0                          0.00
666778888          Nan Vulmer      3.00
444558888           Bill Kats      2.50
222334444          Mary Jones      3.26
111223333          John Smith      3.45

Total number of students: 4
Average GPA: 3.05

Originally Posted by vart

there is not element with index i

what does that mean?

im doing something wrong, because i tried changing it to

for (int j = i; j >0; j--)

and it made it worse... im not sure i understand.

the int j= i?

oh. crap. alright, thank you.