new and delete with multi_dimension array

[slscus]

I need to dynamically generate a multi_demension array. I know
how to do it with calloc() and free(), Could you tell me how to
do it with new() and delete()?

Thanks

//Code:

// Memory allocation
int *** pSomething

pSomething = (int ***)calloc(n1, sizeof(int **));
for(int i=0; i<n1; i++) {
pSomething[i] = (int **)calloc(n1, sizeof(int **));
for(int j=0; j<n2; j++) {
pSomething[i][j] = (int *)calloc(n2, sizeof(int *));
}
}

//free

for(int i=0; i<n1; i++) {
for(int j=0; j<n2; j++) {
free pSomeThing[i][j];
}
free pSomeThing[i];
}
free pSomeThing;

//End of the code

[Yves M]

Well, hum, I don't like this way of accessing arrays. My c-style arrays are always :

long *pArray;
long xdim, ydim, zdim;

pArray = (long *) calloc(sizeof(long) * xdim * ydim * zdim);

this translates well when using new instead of calloc.

To quote the standard STL response, you could use std::vector and write a wrapper class for a three dimensional array.

[slscus]

Thanks, but if I did this way, I cann't access the data by using
pArray[i][j][k]. ???

[PaulWendt]

Hi,
If you're interested in multi-dimensional vectors, check out this
old codeguru posting:
http://www.codeguru.com/forum/showthread.php?s=&threadid=210478&highlight=vector+operator

Here's a link from the last discussion that is relevant:
http://www.cuj.com/articles/2000/0012/0012c/0012c.htm

--Paul

[Yves M]

Originally posted by slscus
Thanks, but if I did this way, I cann't access the data by using
pArray[i][j][k]. ???

True, you'll have to do pArray[((i * ydim) + j) * zdim + k];
It's a bit uglier, but not a real problem.

But have a look at the links provided by Paul, you'll get a lot of benefits for using that. Not the least is that you'll get an introduction to STL if you don't know it already ;)

[room_yuy]

quote from Yves:

code:--------------------------------------------------------------------------------
long *pArray;
long xdim, ydim, zdim;

pArray = (long *) calloc(sizeof(long) * xdim * ydim * zdim);
--------------------------------------------------------------------------------


i think should be
-------------------------------------------------------------------------------
const long xdim=NUMBERx,ydim=NUMBERy,zdim=NUMBERz;
long *pArray=new long[xdim*ydim*zdim];
......

delete [] pArray
---------------------------------------------------------------------------------

[JamesSchumacher]

#include <windows.h>
#include <iostream>
#include <stdlib.h>
#include <time.h>

int main(int _argc,char * _argv[]) throw()
{
srand(::GetTickCount());
int *** pPointerToPointerOfPointers = new int **[10];
for (int i = 0; i < 10; ++i)
{
pPointerToPointerOfPointers[i] = new int *[10];
for (int x = 0; x < 10; ++x)
{
pPointerToPointerOfPointers[i][x] = new int(rand());
}
}
for (int p = 0; p < 10; ++p)
{
for (int q = 0; q < 10; ++q)
{
std::cout << "The value of at index " << q << " of the index " << p << " is " << *(pPointerToPointerOfPointers[p][q]) << std::endl;
}
}
// deletion
for (int r = 0; r < 10; ++r)
{
for (int s = 0; s < 10; ++s)
{
delete pPointerToPointerOfPointers[r][s];
}
delete [] pPointerToPointerOfPointers[r];
}
delete [] pPointerToPointerOfPointers;
return 0;
}


That answers the question - using new and delete to accomplish this. (The question was not about std::vector - although, that is a viable solution to what he wants to do - but he asked for new/delete) It is best to answer how to do something, the way the person asks how to do it - that's what he asked for. In this case, it's a question of C++ logic - knowing the answer and understanding how it works will make a better programmer.