Considering a process is allocated megabytes of memory when it runs, worrying about a few thousand kilobytes of wasted space is not really productive.

Wasting memory or wasting CPU resources is never good, of course, but correctness is the first priority. Once you have a solution that works correctly, tighten up memory use, IF it presents a problem in the number of instances you can run; tighten up the algorithmns involved, IF there's a problem with run time.

No problem? Go on to the next task.