Thread: Dynamic array not working

I have used some info from a previous thread. I still can't get it to work, I want to make a 5 by 5 dynamically allocated array. The reason it is dynamic, because in the finished program the dimensions will e specified by the user. Anyhow here is the code:

Code:

#ifndef _GRIDWORLD_H
#define _GRIDWORLD_H

#include "DLList.h"
#include "personarray.h"

class CGridworld
{
  public:

    CGridworld(int nrows=5, int ncols=5);//constructor with gridsize
    //~CGridworld();

    void move(int pid, int new_row, int new_col); //move person pid to 
						  //  (new_row,new_col)
    void printMembers(int i, int j);	//print the people in district (i, j)

  private:

    int **Grid;			//two-dimentional array
    int nrows;			//number of rows in this grid world
    int ncols;			//number of columns in this grid world
    //CPersonArray P;	//stores person info
};

#endif

//============GRIDWORLD.CPP
#include <iostream>
using namespace std;
#include "gridworld.h"


CGridworld::CGridworld( int nrows, int ncols)
{
	Grid = new int *[nrows];

	for( int i = 1; i < nrows; i++){
		Grid[i] = new int[ncols];
	}

	for(int j = 1; j < nrows; j++){
		Grid[j] = 0; //initializing the whole grid to zero
		cout << Grid[j] << endl;
	}
}

right now the code gives me 8 cols and 5 rows
any ideas,

axon

Code:

	for(int j = 1; j < nrows; j++){
		Grid[j] = 0; //initializing the whole grid to zero
		cout << Grid[j] << endl;
	}

Herein lies a problem. Grid[j] is an int*, remember. So what you are doing is, after allocating a bunch of arrays pointed to by these pointers, you set all of the pointers to null, thereby leaking memory. Additionally, arrays are 0-based.

You need a nested loop:

Code:

for(int j = 0; j < nrows; j++){
  for(int k = 0; k < ncols; k++){
    Grid[j][k] = 0; //initializing the whole grid to zero
    cout << Grid[j][k] << endl;
  }
}

ok, that does work, thanks very much, but I am still left with only 20 elements, where I should have 25 with rows and cols being set to 5 each

axon

//EDIT:

actually 24 with i=0.

//EDIT2:

everything is fine now...THANKS!