Newbie learning sorting algorithms and arrays

I am trying to create a program which read data and sorts it out, the data file contains id and grades of those ids and i am have to sort by order of grade and move the id with it, here is where i got so far but it is not working for me.

thanks in advance

Code:

---

#include <iomanip>
#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main ()
{
        int n,f,j,id[12],i;
        double grade[12],hold;
        ifstream input;

       
        for (f=0;f<12;f++)
        {
                input >> id[f];
                input >> grade[f];
        }
        for (j=0; j<12; j++)
        {
                for (i=0; i<12; i++);
                {
                        if (grade[i-1] > grade[i])
                        {
                                hold = grade[i];
                                grade [i-1] = grade[i];
                                grade[i] = hold;
                        }
                        cout << grade[i] << "\n";
                }
        }
        input.close();
        system ("pause");
        return 0;
}

---

Code:

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input >> id[12];
input >> grade[12];

---

Are you going to put everything in a non-existing element ? 12 elements means from 0 to 11.

This thread is a duplicate of Newbie learning sorting algorithms and arrays.

i was trying to delete the other one since its a wrong section of the forum but i cant find the option to delete it.

@ Skizmo

yea i noticed i messed up there i have change it to this

Code:

---

        for (f=0;f<=n;f++);
        {
                input >> id[f];
                input >> grade[f];
        }

---

It helps if you actually read something from the file ;)

but i have the command here or am i missing something :)

Code:

---

ifstream input;
                       
        input.open("data.txt");
        cout << "read how many entries" << endl;
        cin >> n;
       
        for (f=0;f<=n;f++);
        {
                input >> id[f];
                input >> grade[f];
        }

---

Oops... my bad :blush:

its all good, its monday lol, but something is still wrong and i cant figure out what

Your sorting algorithm is wrong. Take a look at these:
http://mathbits.com/MathBits/CompSci/Arrays/Arrays1.htm
Mainly the topics from Bubble sort to Selection sort since they are the simplest.

i changed it to this but not it only reads the fist set of data of the file

Code:

---

#include <iomanip>
#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main ()
{
        int f,j,id[12],i;
        double grade[12],hold;
        ifstream input;
                       
        input.open("data.txt");
               
        for (f=0;f<=12;f++);
        {
                input >> id[f];
                input >> grade[f];
        }
        for (j=0; j<=12; j++);
        {
                for (i=0; i<=12; i++);
                {
                        if (grade[i+1] > grade[i])
                        {
                                hold = grade[i];
                                grade [i] = grade[i+1];
                                grade[i+1] = hold;
                        }
                        cout << grade[i] << "\n";
                }
        }
        input.close();
        system ("pause");
        return 0;
}

---

All your loops have an empty body

Code:

---

        for (f=0;f<=12;f++);  // remove semicolon

---

Also should the condition be f < 12; because there are only 12 elements.

In the other loops you even access the elements with index 13 ( e.g. grade [i] = grade[i+1]; )

You should swap the id elements as well.

Kurt

finally got it to work but now i have a question how would i add names for the program to read? my professor said we cannot use string with arrays

thanks in advance

Quote:

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Originally Posted by peste19

my professor said we cannot use string with arrays

---

If he said it cannot be done then he lied. If he said you shouldn't then he's trying to make your life harder then necessary.
So what are you supposed to use for the names ?
Kurt

[ moved thread ]

Quote:

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Originally Posted by peste19

my professor said we cannot use string with arrays
thanks in advance

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if you can't use arrays and strings you can still use pointers :)
but I believe you've understood your professor incorrectly