Classic problem, I'd done it before, but there's always that moment where you second-guess whether to reach for a doubly linked list plus hashmap or try to get clever.
Start by clarifying the requirements and constraints, then propose using a hash map combined with a doubly linked list to achieve O(1) operations. Explain the design, walk through an example, and discuss edge cases and potential optimizations.
Pro tip: Mention that you would use a doubly linked list to maintain recency order and a hash map for O(1) access, and highlight that this is a common design for systems like databases and caches. Also, discuss thread-safety if the cache might be accessed concurrently.
Ask about expected cache size, eviction policy details, and whether thread-safety is needed. Confirm that both get and put must be O(1).
Suggest using a hash map for O(1) key lookup and a doubly linked list to track usage order. Explain how they work together.
Describe how get moves the accessed node to the front, and put inserts or updates a node, evicting the least recently used (tail) if capacity is exceeded.
Trace through a sequence of get and put operations to demonstrate correctness and O(1) behavior.
Cover scenarios like cache size 0 or 1, updating existing keys, and potential thread-safety using locks or concurrent data structures.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.