I'm having kinda of a difficult time visualizing your data, but it looks like you are scanning over @sortedKeys multiple times. Could you rearrange the logic to scan outward from the current item instead of continually scanning over @sortedKeys?

If you could provide a small bit of code that actually uses this sub, giving it data and showing us the expected outcome it might be a fun challenge for some of us! ;) It could be a significantly smaller set of data than you are working with, just enough to show the input/output is working correctly.

Good luck!