Refactoring

Refactor the code below for readability and maintainability without changing its behavior. Improve naming, reduce nesting, and remove duplication. Keep it idiomatic for the language. Return the refactored code, then a short list of what you changed and why. Code: [PASTE]

The code below is slow / resource-heavy. Identify the bottleneck, explain why it's costly (time/space complexity), and give me an optimized version. Note the tradeoffs of your approach. Code: [PASTE]