Using malloc for allocation of multi-dimensional arrays with different row lengths

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First, you need to allocate array of pointers like char **c = malloc( N * sizeof( char* )), then allocate each row with a separate call to malloc, probably in the loop:


/* N is the number of rows  */
/* note: c is char** */
if (( c = malloc( N*sizeof( char* ))) == NULL )
{ /* error */ }

for ( i = 0; i < N; i++ )
{
  /* x_i here is the size of given row, no need to
   * multiply by sizeof( char ), it's always 1
   */
  if (( c[i] = malloc( x_i )) == NULL )
  { /* error */ }

  /* probably init the row here */
}

/* access matrix elements: c[i] give you a pointer
 * to the row array, c[i][j] indexes an element
 */
c[i][j] = 'a';

If you know the total number of elements (e.g. N*M) you can do this in a single allocation.

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