Thread: Array with user-defined dimensions

  1. #1
    Registered User
    Join Date
    Oct 2003

    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:

    #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";
    	for (i = 0; i < rows; i++, counter++)
    		if (!(pColumns = new int[columns]))
    			cout << "Not enough memory. Sorry.\n";
    		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?


  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    > 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.
    If at first you don't succeed, try writing your phone number on the exam paper.

  3. #3
    Registered User
    Join Date
    Oct 2003
    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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