Question

I’m working on a program which reads some data from a file formatted like so:

21
285 270 272 126 160 103 1
31 
198 180 163 89 94 47 1 
32
240 230 208 179 163 104 1
33
15 13 12 14 15 15 0
34
63 61 62 24 23 20 2

I’m trying to read the first number into one pointer array and the other 7 numbers into a parallel two dimensional pointer array but for some reason, every time I run my code it just stops working. It’s not returning an error but I feel like my pointer usage is wrong because this is my first time using pointers. The data file is called “election_data_121.txt”, fyi. Heres the code. If anyone could take a look I’d be so grateful:

#include <iostream>
#include <fstream>
using namespace std;

//bool openFileIn(fstream &, char *);

int main()
{
    const int PREC_SIZE = 30;
    const int CANIDATES = 7;
    int *precinct_num[PREC_SIZE];
    int *num_votes[PREC_SIZE][CANIDATES];
    cout << "Declarations made." << endl;

    fstream dataFile; //Make a file handle
    cout << "File object made." << endl;
    //Open the file and check that it opened correctly
    if(!openFileIn(dataFile, "election_data_121.txt"))
    {
        cout << "File open error!" << endl;
        return 0; //Exit the program
    }

    cout << "File opened." << endl;

    //Read the contents of the file into the proper arrays
    int counter = 0;
    while(!dataFile.eof()) 
    {
        dataFile >> *precinct_num[counter];
        for(int i = 0; i < 7; i++)
        {
            dataFile >> *num_votes[counter][i];
        }
        counter++;
    }

    //Print out the data
    for(int j = 0; j < counter; j++)
    {
        cout << *precinct_num[j];
        for(int i = 0; i < 7; i++)
        {
            cout << *num_votes[j][i];
        }
    }

    dataFile.close();
    cout << "End of file";
    return 0;
}

bool openFileIn(fstream &file, char *name)
{
    file.open(name, ios::in);
    if(file.fail())
        return false;
    else
        return true;
}

Thanks again!

Answer 1

This code doesn’t need pointers at all; why would you think it does? Just change the types of precinct_num and num_votes and stop dereferencing them and I think (at a glance) that it should be fine.

#include <iostream>
#include <fstream>
using namespace std;

//bool openFileIn(fstream &, char *);

int main()
{
    const int PREC_SIZE = 30;
    const int CANIDATES = 7;
    int precinct_num[PREC_SIZE];
    int num_votes[PREC_SIZE][CANIDATES];
    cout << "Declarations made." << endl;

    fstream dataFile; //Make a file handle
    cout << "File object made." << endl;
    //Open the file and check that it opened correctly
    if(!openFileIn(dataFile, "election_data_121.txt"))
    {
        cout << "File open error!" << endl;
        return 0; //Exit the program
    }

    cout << "File opened." << endl;

    //Read the contents of the file into the proper arrays
    int counter = 0;
    while(!dataFile.eof()) 
    {
        dataFile >> precinct_num[counter];
        for(int i = 0; i < 7; i++)
        {
            dataFile >> num_votes[counter][i];
        }
        counter++;
    }

    //Print out the data
    for(int j = 0; j < counter; j++)
    {
        cout << precinct_num[j];
        for(int i = 0; i < 7; i++)
        {
            cout << num_votes[j][i];
        }
    }

    dataFile.close();
    cout << "End of file";
    return 0;
}

bool openFileIn(fstream &file, char *name)
{
    file.open(name, ios::in);
    return !file.fail();
}