refactor: making function hill more clear

[allrob23]

While reviewing the hill method, I noticed an opportunity to enhance its readability and clarity. This refactor replaces the list-based contents with a set for more intuitive element handling and removes unnecessary early sorting, deferring it to when "others" are processed.

Changes:

• Changed contents = list(aa.keys()) to contents = set(aa.keys()) for clearer element management.
• Removed contents.sort() and used sorted(contents - {'e'}) for alphabetical processing of "others."
• Used contents.remove(this) for 'C' and 'H' to avoid reprocessing, simplifying the loop for "others."

Benefits:

• Readability: The code is more concise and easier to follow, with set operations aligning with the method intent.
• Complexity: Set operations (e.g., remove, difference) are O(1) on average, compared to O(N) for list searches, though the impact is minor given the small number of elements in most cases.

The behavior and output of the hill method remain unchanged. This refactor makes the code more maintainable without affecting functionality.