Read integers from a text file into a two-dimensional array and assess the length

Question

I need to read integers from a text file into a two-dimensional array.

-1 indicates the end of array. Every array supposes to have 6 positive integers (-1 does NOT count as part of the array).

For example, if my text file contains the following integers:

1 3 4 6 1 7 -1 1 3 5 7 2 3 -1 2 5 7 2 6 3 -1

That means when these integers are read into the program, there will be 3 arrays:

1st Array: 1 3 4 6 1 7

2nd Array: 1 3 5 7 2 3

3rd Array: 2 5 7 2 6 3

I wrote a program to assess if each array has a correct length (6 integers) AND correct integers (all integers should be positive) and output corresponding error messages if these criteria are not met.

#include <iostream>
#include  <fstream>
#include <string>
#define MAX_ROWS  3
#define MAX_COLUMNS 2

using namespace std;

int main()
{
    string fileName = "testdata.txt";                                                           //declare a string to store the Input File's name 
    ifstream inFile;                                                                             //name the input file connection 
    inFile.open(fileName);                                                                       //open the Input File
    string errorMessage = "Input file cannot be found";                                           //Declare a string to store an error message, just in case the Input file doesn't exist or cannot be found

    if (!inFile) {                                                                               //If the Input File doesn't not exist, then display the error message
        cout << errorMessage << '\n';                                                           //also store the error message to the Output file
        system("pause");
        return  0;                                                                               //end the program if the Input File does not exist
    }


    int checkNbr;
    int ArrB[MAX_ROWS][MAX_COLUMNS];
    int size = MAX_ROWS * MAX_COLUMNS;
    bool bad = false;
    bool invalidnum = false;

while (!inFile.eof())      
    {
        for (int i = 0; i < MAX_ROWS;i++) {
            for (int j = 0; j < MAX_COLUMNS; j++) {
                inFile >> ArrB[i][j];
                if (ArrB[i][j] == -1) {
                    bad = true;
                    cout << "\nThe array does not have enough integers" << endl;
                    break;
                    //return 1;
                }
                else {
                    if (ArrB[i][j] < 1) {
                        invalidnum = true;
                    }
                }
                cout << *(*(ArrB + i) + j) << " ";

            }
        }

        if (invalidnum == true) {
            invalidnum = false;
            cout << "\nThere is/are negative number(s) or zero(s) in the array imported from your text file.\n";
        }

        if (bad == false) {
            inFile >> checkNbr;
            if (checkNbr == -1) {
                cout << "\nThe size of the array is correct." << endl;
            }
            else {

                while (checkNbr != -1)
                {
                    cout << checkNbr;
                    cout << " ";
                    inFile >> checkNbr;

                }

                cout << "\nYou have too many numbers in this array\n";
            }
        }
    }

    return 0;
}

If I run my program:

Case 1 - PASSED

1 2 3 4 5 6 -1 3 5 2 1 6 8 3 2 5 -1 3 3 5 6 7 5 -1

Case 2 – PASSED

1 2 3 4 5 -6 -1 3 -5 2 1 6 8 -1 3 5 6 7 5 -1

Case 3 – FAILED(!)

1 2 3 4 -1 1 2 3 4 5 6 7 8 -1 1 2 3 4 5 -1

As you can see, case 3 failed. The second array (1 2 3 4 5 6 7 8) is actually longer than the declared array size, but it’s printing out “The array does not have enough integers” error message…..

The ONLY time this program won't work is when the first array does not have enough integers.

Any comments or hints would be appreciated!

Answer 1

The problem

bad is not reset after processing it.

Solution

Move bool bad = false; into the while (!inFile.eof()) loop body so it gets reset every iteration. If you define variables with the narrowest possible scope you can usually avoid this problem, so you should strongly consider doing the same thing with the rest of your variables.

This will solve the bug that was asked about and at least one other bug you haven't found yet. This leaves at least two more outstanding bugs for you to resolve, and both have been covered in the question's comments.

TL;DR version

A quick walk through of input 1 2 3 4 -1 1 2 3 4 5 6 7 8 -1 1 2 3 4 5 -1

1 2 3 4 -1 is parsed and found to be bad, so bad is set to true and the testing for a too-long value and clean-up is skipped. The file hasn't ended, so the program loops and starts reading the next array.

input remaining:

 1 2 3 4 5 6 7 8 -1 1 2 3 4 5 -1

output so far:

1 2 3 4 
The array does not have enough integers

1 2 3 4 5 6 is parsed. This fills the array and the for loops exit. bad is still true, so the check for overflow is skipped and no message is printed.

Input remaining:

 7 8 -1 1 2 3 4 5 -1

output so far:

1 2 3 4 
The array does not have enough integers
1 2 3 4 5 6

Now 7 8 -1 is parsed. This is too short to be an array and reported. Take careful note of what this does to the output.

Input remaining:

 1 2 3 4 5 -1

output so far:

1 2 3 4 
The array does not have enough integers
1 2 3 4 5 6 7 8 
The array does not have enough integers

Whoops. Looks like 1 2 3 4 5 6 7 8, not merely 7 8, was too short.

the program then parses 1 2 3 4 5 and finds it to be too short.

Input remaining:

output so far:

1 2 3 4 
The array does not have enough integers
1 2 3 4 5 6 7 8 
The array does not have enough integers
1 2 3 4 5 
The array does not have enough integers