LeetCode Card 348 — Design and LRU Cache / Structure
Pattern signal
This pattern usually appears when the prompt involves object behavior, custom API semantics, and data-structure composition. LRU Cache, Min Stack, randomized set, and iterator or scheduler design prompts fit here.
What Structure means here
In BASIC, the Structure step is where you state the invariant, helper contract, or control-flow skeleton before coding. For Design and LRU Cache, that matters because the pattern only becomes useful once the candidate is explicit about what is being tracked, reduced, or preserved.
Interview move
A strong move is to make the plan visible before full execution. In this pattern family, say out loud what representation makes the problem easier: the map entry, the pointer invariant, the recursion contract, the queue contents, or the DP state. That keeps the implementation attached to a reason.
Common miss
The miss is focusing on method signatures before deciding the core invariants and representation. BASIC reduces that risk because the stage sequence forces you to earn the implementation instead of jumping straight into it.
BASIC prompt
“Given that this looks like Design and LRU Cache, what is the simplest way to state the invariant, helper contract, or control-flow skeleton before coding?”