First, clarify the existing file system's data structures and how file sizes are stored. Then, design the methods to check preconditions (existence, compression state) before modifying size, ensuring idempotency and proper return values. Finally, discuss potential edge cases and trade-offs, such as handling concurrent access or large files.
Pro tip: Mention that you would store a boolean flag or use a sentinel value (e.g., negative size) to track compression state, and consider thread-safety if the file system is shared. This shows awareness of real-world constraints beyond the basic requirements.
Ask about the file system's existing API, how file sizes are represented, and whether compression state is already tracked. Confirm expected behavior for edge cases like zero-size files or repeated calls.
Determine if you need to add a compression flag to the file object or infer state from size. Consider using a separate set to track compressed files if modifying the file structure is not allowed.
Write pseudocode for both methods: check existence, check current compression state, update size (halve or double), and update compression flag. Return false if preconditions fail.
Address cases like file not found, already compressed/decompressed, zero-size files, and potential integer overflow. Discuss how to handle concurrent access if needed.
State time and space complexity (O(1) for hash map lookups). Discuss trade-offs of storing compression state versus inferring it, and any impact on existing operations.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.