London | 26-Jul-SDC | Roman Sanaye | Sprint 2 | Improve code with pre-computing

[RomanSanaye]

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Task code

CYF-1183

Changelist

• Optimized find_longest_common_prefix by introducing lexicographical sorting as a pre-computation step.
• Reduced time complexity from $O(N^2)$ to $O(N \log N)$, enabling large datasets (such as the 1-million-item test case) to pass efficiently.
• Left the existing test suite and helper functions completely untouched as required.

[cjyuan]

• Could you use complexity to explain how the new implementation is better than the original implementation?

• Could you also improve the implementation in count_letters?

[RomanSanaye]

Hi @cjyuan ,
Thanks for the feedback!

1. Longest Common Prefix:** I've added a comment explaining how sorting the list first allows us to check only adjacent pairs, reducing the time complexity from O(N^2) to O(N log N).
2. count_letters: I've refactored the function to use sets for character collection. By replacing the inner string search (in s) with O(1) set lookups, the time complexity drops from O(N^2) to O(N).

[cjyuan]

Well done!