Question

Say I have a dynamic array like:

int* integers = new int[100];

Is there a way to delete only part of the array such as:

int* integers2 = integers + 50;
delete[] integers2;

I want to not only delete everything 50 and beyond, but if I call another delete[] on the original integers array, then it would only delete the correct amount of memory and not try to delete the originally allocated amount and seg fault.

Why I want to do this: I have a data structure that is structured in levels of arrays, and I want to be able to create this data structure from a full array. So I want to be able to say

int* level1 = integers;
int* level2 = integers + 50;
int* level3 = integers + 100;

But when level 3 is no longer needed, the data structure will automatically delete[] level3. I need to know that this will behave correctly and not just destroy everything in the array. If it will then I need to just create new arrays and copy the contents over, but it would be nice to avoid doing that for performance reasons.

Edit: Everyone seems to be jumping to the conclusion that I just should use a dynamic resizing container (ie vector, deque) in the first place for my data structure. I am using levels of arrays for a good reason (and they aren’t equally sized like I make it look like in my example). I was merely looking for a good way to have a constructor to my data structure that takes in an array or vector and not need to copy the original contents over into the new data structure.

Answer 1

No, this will not behave correctly. You can only delete[] pointers that you got from new[], else the results are undefined and bad things might happen.

If you really need the array to get smaller you have to allocate a new one and copy the contents manually.