Tried to brute-force my way through it with arrays and a hash table but couldn't land on a clean solution.
Start by clarifying the exact validation criteria (e.g., length, character set, format, uniqueness) and edge cases with the interviewer. Then propose an efficient algorithm, likely using a hash set for O(1) lookups and string manipulation, and analyze time/space complexity. Finally, discuss potential optimizations and test with examples.
Pro tip: Demonstrate Amazon's Leadership Principles by proactively discussing trade-offs (e.g., between strict validation and performance) and suggesting how to handle invalid inputs gracefully, showing customer obsession and ownership.
Ask questions to understand the exact criteria for a valid promo code, such as length, allowed characters, format (e.g., regex), and whether codes must be unique. Confirm input/output format and edge cases.
Choose appropriate data structures (e.g., hash set for uniqueness, regex for pattern matching) and outline the validation steps. Consider iterating through each code and applying checks.
Determine time and space complexity. Typically O(n * m) where n is number of codes and m is average code length, but can be optimized with early termination.
Discuss handling empty input, null values, duplicate codes, and codes that are too long/short. Decide on error handling or filtering.
Walk through test cases (valid, invalid, edge) and suggest possible optimizations, such as precompiling regex or using bitwise operations for character checks.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.