matrices with malloc

[Shotgun]

Hi, I want to know how to create a interger matrix of [n] rows and [m] columns with malloc.

any ideas

    *matix = malloc ( sizeof (int) * n );
    if ( matrix == NULL )
    exit ( EXIT_FAILURE ); /* Memory could not be allocated, so exit. */

creates an array of length [n]
I know I want to create an array [n] long of arrays [m] long but I really have no idea of how to do it...

help me please

[xeddiex]

You already asked this question in another thread. Please be more patient next time.

[Shotgun]

Yer I did, sorry and thanks at the same time

to clarify some questions are these equivalent

*array (equiv too) array[]
**matrix (equiv too) matrix[][]

if so, I recon I understand it

[xeddiex]

Yer I did, sorry and thanks at the same time

to clarify some questions are these equivalent

*array (equiv too) array[]
**matrix (equiv too) matrix[][]

if so, I recon I understand it

Yes. But just incase you don't know how to use the last one in pointer notation correctly, here's how:

*((*(matrix + row)) + col) = 5;

The parenthesis sets the precedence, starting from the inner most and left to right. Or, you could make it easy on yourself and just do:

matrix[row][col] = 5;

[Shotgun]

This is my current code
NOTE: totalCustomers is # of rows and totalProducts is # of columns

    int **matrix;

    **matrix = malloc ( sizeof (int) * totalCustomers );

    for ( i=0; i < totalCustomers; i++ )
     {
       matrix[i] = malloc ( sizeof (int) * totalProducts );
     }

I am getting a seg fault on the first malloc
also when i compile i also get a warning

assignment makes integer from pointer without a cast

any ideas...
Thanks

[SlyMaelstrom]

Ahem... A more accurate answer.

[xeddiex]

This is my current code
NOTE: totalCustomers is # of rows and totalProducts is # of columns

    int **matrix;

    **matrix = malloc ( sizeof (int) * totalCustomers );

    for ( i=0; i < totalCustomers; i++ )
     {
       matrix[i] = malloc ( sizeof (int) * totalProducts );
     }

I am getting a seg fault on the first malloc
also when i compile i also get a warning

any ideas...
Thanks

What's in bold above is your problem. You don't double-dereference, you just use the matrix variable itself: matrix = malloc(....).