How would you design LRU cache operations for O(1)?
PICTURE THIS: HASH MAP
Simple meaning
Hash map to nodes plus doubly linked list for recency.
WHY — System instead of guessing?
Why interviewers care about System:
question about System.
trade-offs, and what you would actually do on a DSA project - not buzzwords.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Hash map to nodes
plus doubly linked list for recency.
- 2Get and put update
the list ends.
- 3How it works
Interviews expect both structures together.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Hash map to nodes plus doubly linked list for recency. Get and put update the list ends.