Optimising list insertions

I've got a script I'm writing which merges two lists together, or more specifically, if the two lists are A and B, then B is merged into A. However, I have issues with memory usage and speed.

Now, for the majority of cases I think memory usage is fine, I've been using the list-memory hack to keep most operations good. But the main problem I'm having is in the case of where I'm inserting elements of B into list A (opposed to appending them).

My code does nothing complex, it decides where in A the result should go and then does an llListInsertList(). Now, my question is, are there any good ways to optimise list insertion?

For example, would I be better using a third list and appending items from A and B to it, rather than using llListInsertList? The main problem for me being that in a worst-case scenario I have to perform llListInsertList for every single element in B, which of course I'd rather not do =)

Anyone attempted similar problems and have any solutions that might be useful?

I believe this should work:

A = llListInsertList((A=[])+A, B, pos);

If you can append them and use llListSort, thats what I would recommend you do.

Something like:
A = llListSort(((B = A = [])+ A) + B, 1, TRUE);

Thanks for the suggestion Hewee, it solved the memory issue but unfortunately too many llListInsertList() calls are still killer on performance.

Cheers Strife for pointing me back to llListSort! After managing to make enough room to fit my A and B lists it is a much faster solution! Had to do a bit of fiddling to get it to sort my particular lists, but it works pretty well now. I have about 50 bytes free memory now but my memory usage never goes higher than that, though still can't wait for Mono =D