data-structuresEASYDATA STRUCTURE VISUALIZATION
Warm up with LRU cache core
Easy Data Structures arena: hash map plus doubly linked list invariants
XP reward
90
Coins
8
Target time
12m
A feature flag service needs O(1) reads and evictions under heavy traffic. You are working inside an interview-style data structure lab, and the arena only clears when the result is safe, deterministic, and explainable.
Learning objective
Learn to apply hash map plus doubly linked list invariants in an interview-style data structure lab while explaining the invariant, safety constraints, and hidden edge cases.
Mission order
Operations are GET key and PUT key value with a fixed capacity. Implement the direct solution first, then document the one edge case that can break it. Submit the solution plus enough reasoning to pass hidden edge cases.Visible checks
sample case
Expected: 2
empty input
Expected: 0
Clear requirements
- Demonstrates hash map plus doubly linked list invariants
- Handles the visible sample and hidden edge cases
- Keeps output deterministic and explainable
- Avoids unsafe dynamic execution
Secure validation contract
Judge type
DATA STRUCTURE VISUALIZATION
Complexity target
Readable O(n) or O(n log n) baseline
Workspace
Structure lab
root
left
right
leaf A
leaf B
Test Results
Run the visible checks when your first pass is ready.
Clear Protocol
1Read the scenario and restate the expected output shape.
2Run visible checks before chasing hidden edge cases.
3Use Genie for one nudge if stuck, then explain the invariant.
4Submit only when the result is deterministic and safe.
Rewards
XP
90
Coins
8
Mission Route
Hints
Hints are metered and logged for No Hint Hero runs.
Genie Mentor Core
Hint protocol / contextual guardrails active
Progressive hints
Failed-test aware
Solution guarded
Mission: data-structures-easy-lru-cache0 attempts0 failed tests0 hints used
Progressive hint depth
Genie: Genie online. I use your mission, attempts, failed tests, hints, and path context to coach the next rep without dumping answers first.