The rules part felt obvious once I started coding but the ordering piece is where I fumbled a bit.
Start by clarifying the matching rules and ordering criterion, then design a function that filters candidate transactions based on the rules and selects the best one according to the ordering. Discuss trade-offs between different implementations, such as sorting versus iterative comparison, and consider edge cases like no matches or multiple matches.
Pro tip: Emphasize the importance of defining a clear and deterministic ordering criterion to avoid ambiguity, and mention how you would handle ties or conflicting rules. Also, discuss how you would test the function with unit tests covering various scenarios.
Ask questions to understand the matching rules (e.g., exact match on amount, date range, currency) and the ordering criterion (e.g., most recent, highest amount). Confirm what 'best' means and how ties are broken.
Outline a plan: iterate through candidate transactions, apply matching rules to filter, then select the best using the ordering criterion. Consider whether to sort or use a single pass with a comparator.
Discuss time and space complexity of your approach. Compare sorting (O(n log n)) versus iterative best-finding (O(n)). Mention any assumptions about input size or rule complexity.
Address scenarios like no matching transactions (return null), multiple matches with equal ordering (tie-breaking), and invalid inputs. Explain how you would validate inputs.
Describe how you would test the function: unit tests for typical cases, edge cases, and performance. Mention the importance of deterministic behavior.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.