[SOLVED] 2D dynamic array, less code maybe?

Fritz_Doll · 10-14-2011, 06:17 PM

Language: C
Is there a shorter way to do the following
m, n are generic values, where m is a constant and n is a variable.
type is any primitive.

Code:

type **k=calloc(n,sizeof(type*));
for(i=0;i<n;i++)
  k[i]=calloc(m,sizeof(type));

Or am I stuck with this, and should just write a function?

ta0kira · 10-14-2011, 07:15 PM

You can calloc an array of size n*m then access the (i,j) element with i*m+j.
Kevin Barry

ArthurSittler · 10-14-2011, 07:43 PM

Do you want a 2D array of the type or of pointers to the type?

You can allocate the entire array at once with a single call:

ArrayName = calloc( m * n * sizeof( type ) );

malloc() may be faster than calloc() because it does not initialize the memory. If you are sure that you will not try to read from any element before you have initialized it, this could save time.

Please read the man pages or the descriptions of the functions to make sure that my recall of this information is not faulty.

If the array index size n will change after your first allocation then you can realloc() to change the array size. This preserves the contents of your array while giving you more or fewer elements.

Fritz_Doll · 10-14-2011, 08:32 PM

Thanks for the feed back.
Guess I forgot about treating 1D arrays as 2D.
I'll have to try to remember that.