Question

Consider the following C++ code example:

int array_1[] = {5,6,7};
int array_2[] = {6,7,8,9};
int array_3[] = {2,3};

int* meta_array[] = {array_1, array_2, array3};

Now I want to iterate over all of the elements in the sub arrays of meta_array without causing a seg fault.

The problem, of course, is that I have no way to get the size of the arrays to avoid overstepping their bounds.

I can do sizeof array_1 / sizeof array_1[0] to get the size of a common 1-dimensional array pretty quickly, but once I’m in the meta_array, every element has been converted to a pointer, and so sizeof will return the byte size of the pointer instead of the entire array. Thus, sizeof meta_array[0] / sizeof meta_array[0][0] doesn’t really do much to help my cause.

Is there a standard solution to iterating over nonuniform multidimensional arrays out there already, or should I just go ahead and use std::vector?

Answer 1

use std::vector.

or, use a “closing” number but you must be sure there will be no elements with that value, ever.

int array_1[] = {5,6,7,-1};
int array_2[] = {6,7,8,9,-1};
int array_3[] = {2,3,-1};

int*  meta_array[] = 
{
  array_1, 
  array_2, 
  array_3,
  NULL
};

for(int i=0; meta_array[i] != NULL; ++i)
{
   for(int j=0; meta_array[i][j] != -1; ++j)
       printf("%d",  meta_array[i][j]);
   printf("\n");
}