2D Array Program Help

[newbieCPlusPlus1]

I was assigned to write a program using a 2D array. The code was returned to me with some comments of improvement by the professor. I am unsure how to correct these mistakes.

Here is my original code:

/* Program to fill a two dimensional array, output the array, and determine
   the sum of each column and the sum of each row using loops and functions
   input: Assignment8.dat file
   output: filled array, sum of columns and rows
   processing: use a nested loop to fill the array, void function to output
   the data
*/

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

using namespace std;

const int ROW = 20;
const int COL = 12;

void fillArray(int a[][COL]);
void outputArray(int b[][COL]);
int sumRow(int c[][COL]);
int sumCol(int d[][COL]);
int main()
{

	
	int TwoD[ROW][COL];

	//call to function to fill array
	fillArray(TwoD);

	//call to function to output array
	outputArray(TwoD);

	//output row sum
	sumRow(TwoD);

	//output column sum
	sumCol(TwoD);

	return 0;
}

/* Function to fill a two dimnensional array that may a maximum of contain 25 rows 
   and 15 columns.
   input: a two dimensional array is passed to the function
   output: the filled array is sent back to the function call
   processing: use a nested loop to fill the array
*/

void fillArray(int a[][COL])
{
	ifstream file;
	file.open("Assignment8.dat");

	if (!file.fail()) //test file is opened
	{
		cout << "File correctly opened" << endl;
		file.ignore(18, '\n'); //ignore first row containing actual numbers

		while (!file.eof())
		{
			for (int i = 0; i < ROW; i++)
			{
				for (int j = 0; j < COL; j++)
				{
					file >> a[i][j];
				}
			}
		}
	}
	else
	{
		cout << "Error opening file!" << endl;
		file.close();
	}

}

/* Function to output a 2 dimensional array
   input: the numbers in the array will be output to
   the screen nothing is sent back to the function call
   processing: use a nested loop to output the array
*/

void outputArray(int b[][COL])
{
	for(int i = 0; i < ROW; i++)
	{
		for(int j = 0; j < COL; j++)
		{
			cout << setw(5) << b[i][j];
		}
		cout << endl;

	}
}

/* Function to calculate the sum of each row from a two 
   dimensional ray and return the data to function as
   an array.
   input: a two dimensional array
   output: the sum of each row
   processing: use a nested loop to calculate the sum
   of each row
*/

int sumRow(int c[][COL])
{
	int rowTotal = 0; 
	for (int i = 0; i < ROW; i++)
   {
      for (int j = 0; j < COL; j++)
      {
         rowTotal += c[i][j];
      }
	  cout << "Row " << (i + 1) << " total: " << rowTotal << endl;
	}
	return rowTotal;
}

/* Function to calculate the sum of each column from a two 
   dimensional ray and return the data to function as
   an array.
   input: a two dimensional array
   output: the sum of each column
   processing: use a nested loop to calculate the sum
   of each row
*/

int sumCol(int d[][COL])
{
	int colTotal = 0; 
	for (int j = 0; j < COL; j++)
   {
      for (int i = 0; i < ROW; i++)
      {
         colTotal += d[i][j];
      }
	  cout << "Column " << (j + 1) << " total: " << colTotal << endl;
	}
	return colTotal;
}

Question 1:
The first issue she asks me to correct is instead of directly defining the actual number of rows(20) and columns(12) she wants me to declare the maximum which is 25 rows and 15 columns.

This first screenshot is my original functioning code.
http://i.imgur.com/g8PpGTG.png

This is what happens when I try to change the row and column declaration to the max. How do I prevent this from happening? Is there another way I should code the max?
http://i.imgur.com/J1B6PlT.png

Question 2:
I am supposed to have the program output the actual number of rows and then the actual number of columns in the fill function. How do I achieve this? I am not sure how to begin.

Question 3:
My professor commented "nested loop to fill arrays should only have 2-levels". What does this mean? Isn't my code already only 2-levels? I only have one nested loop inside another.

Question 4:
How do I turn my functions that sums rows and columns into a 1D array that send back to main? I already have the calculation coded, but I don't know how to store this calculation as an array. How would I output the data?

Question 5:
What does this mean? "need to reset sum to 0 between
iterations of out loop in functions to find sums", why is this necessary to do when the function already properly calculates the sums? How do I go about achieving this?


Thanks for all your help. Sorry if this format is not correct for posting.

[tscott8706]

I won't answer all your questions, but I'll get you started on the right track.

Let's look at some code in your fillArray function

		while (!file.eof())
		{
			for (int i = 0; i < ROW; i++)
			{
				for (int j = 0; j < COL; j++)
				{
					file >> a[i][j];
				}
			}
		}

If ROW and COL are larger than the data in the file, which is the case, you are going to be reading bogus data from the file into your array (because the file has already ended, but you keep reading from it). That's why you see those strange numbers in your second screenshot.

For reading data from the file, the ONLY condition needs to be the end of the file. Otherwise you risk reading in data that doesn't exist in the file.

I would suggest you use the getline function if you are allowed. http://www.cplusplus.com/reference/string/string/getline/

Each line will go into c[ROW][whatever column number you are on in that line].

So you will have something similar to this (very much pseudocode):

// while there is still data in the file...
//    get the next line
//    fill up my array from that line
//    increment my row 

Hopefully that help get you on the right track, but let me know what further questions you have.

[newbieCPlusPlus1]

I understand now why it prints the weird output. Unfortunately, we are not allowed to use std::getline since we have not learned it yet.

[tscott8706]

Ok. Then I bet at some point, the next character from the file will be \n (I'm guessing, I'm not 100% certain).

Note this pseudocode makes the assumption that the file will end with a newline character!

So do something like this...

// while there is still data in the file...
//    for or while loop that loops until you reach a newline character
//        set your array[row][col] to the new character if you don't do that in your loop already
//        if you don't increment col in your loop, increment it here
//    loop is over and you found a newline, so now you can increment your row 

The main thing you will need to wrap your head around is that you can't put the const ROW or COL variables in your loop. You will need to depend on something that is in the file... which will probably be the newline character.

[newbieCPlusPlus1]

Thank you I have figured out the first question. Does anyone have input on the other ones?