Q:

Scala which data structure is most efficient for my intended operations?

I am running a dynamic programming function where I carry a list of strings throughout the process.
Over time, I append new strings to the end of this list, and occasionally I may remove the last element. Right now I am currently using a mutable ListBuffer, doing += for the appends and .trimEnd(1) for the removals.
Once my dynamic programming procedure is done, I need to efficiently be able to access each element of that list/sequence/etc, and in order (the first item I inserted will be first accessed, whereas last item I inserted will be the last accessed).
I've also tried ArrayBuffers but they both seem too slow. I am trying to speed this process up and I am wondering if I am using a data structure that has O(n) operations when there may be something that has O(1) time operations for what I need.

A:

A simple singly linked list will provide O(1) for the append/discard portions of what you describe. Worst case, if you need to reverse the list at the end before processing, that would be an O(n) operation paid once.
Note that if you go down this road, during the accumulation phase "first" and "last" will be reversed (you will prepend items and drop the first item by getting the tail of the list).

