Question

This isn’t actually a homework question per se, just a question that keeps nagging me as I do my homework. My book sometimes gives an exercise about rearranging data, and will explicitly say to do it by changing only pointers, not moving the data (for example, in a linked list making use of a “node” struct with a data field and a next/pointer field, only change the next field).

Is it bad form to move data instead? Sometimes it seems to make more sense (either for efficiency or clarity) to move the data from one struct to another instead of changing pointers around, and I guess I’m just wondering if there’s a good reason to avoid doing that, or if the textbook is imposing that constraint to more effectively direct my learning.

Thanks for any thoughts. 🙂

Answer 1

Here are 3 reasons:

Genericness / Maintainability:

If you can get your algorithm to work by modifying pointers only, then it will always work regardless of what kind of data you put in your “node”.

If you do it by modifying data, then your algorithm will be married to your data structure, and may not work if you change your data structure.

Efficiency:

Further, you mention efficiency, and you will be hard-pressed to find a more efficient operation than copying a pointer, which is just an integer, typically already the size of a machine word.

Safety:

And further still, the pointer-manipulation route will not cause confusion with other code which has its own pointers to your data, as @caf points out.