Array with user-defined dimensions

This is a discussion on Array with user-defined dimensions within the C++ Programming forums, part of the General Programming Boards category; Hi. I have a question about a program I wrote to generate a 2D "Array" with user-defined dimensions. Right now ...

  1. #1
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    Question Array with user-defined dimensions

    Hi. I have a question about a program I wrote to generate a 2D "Array" with user-defined dimensions. Right now the program only asks for the dimensions, fills the elements with an ascending sequence of numbers and shows the "array". Here's the code:

    Code:
    #include <iostream>
    #include <cstdlib>
    #include <iomanip>
    
    using namespace std;
    
    int main()
    {
    	int rows;
    	int columns;
    	int i;
    	int j;
    	int counter = 1;
    		
    	cout << "Rows? ";
    	cin >> rows;
    	cout << "Columns? ";
    	cin >> columns;
    	cout << endl;
    
    	int** pRows;
    	int* pColumns;
    	if (!(pRows = new int*[rows]))
    	{
    		cout << "Not enough memory.  Sorry.\n";
    		exit(1);
    	}
    	for (i = 0; i < rows; i++, counter++)
    	{
    		if (!(pColumns = new int[columns]))
    		{
    			cout << "Not enough memory. Sorry.\n";
    			exit(1);
    		}
    		pRows[i] = pColumns;
    		for (j = 0; j < columns; j++, counter++)
    		{
    			pRows[i][j] = counter;
    			if (j == columns - 1) counter--;
    		}
    	}
    
    	for (i = 0; i < rows; i++)
    		for (j = 0; j < columns; j++)
    		{
    			cout << setw(6) << pRows[i][j];
    			if (j == columns - 1) cout << endl;
    		}
    	
    	delete[] pRows;
    	delete[] pColumns;
    	return 0;
    }
    My question is: is it enough with the two delete instructions to free all dynamically allocated memory? I don't think so, since the pointer pColumns goes through different memory allocations inside of the for loop. How can I solve this? Or should I simply ignore the memory leaks?

    Or is there any other way to create a 2D Array with user-defined dimensions?

    Thanks!

  2. #2
    and the hat of wrongness Salem's Avatar
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    > delete[] pColumns;
    But that's just a temp variable, the real variable is pRows[i]

    Which leads onto
    for ( i = 0 ; i < rows ; i++ ) delete [] pRows[i];
    delete [] pRows;
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
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    I wonder how I didn't see that.... lol! Everything is easier once someone explains it to you. Thank you very much!

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