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Problem library
High-level architecture and low-level object design, each with progressive hints, a written analysis, approach and worked solution.
Build constant-time lookup and eviction with a hash map and a doubly linked list.
Model a directory tree with path resolution, safe moves and consistent mutations.
Model reversible commands, history branches and atomic grouped edits.
Coordinate producers and consumers with capacity, deadlines and explicit close semantics.
Evict by access frequency with an LRU tie-break and constant-time bookkeeping.
Model simultaneous movement, food growth and body collisions with clear invariants.
Match methods and path segments with deterministic precedence and safe decoding.
Implement deterministic virtual-node placement and immutable membership snapshots.
Schedule cancellable deadlines with a min-heap, generation tokens and controlled time.
Implement immutable snapshots, compare-and-swap and tombstones in a small MVCC model.
Maintain a heap plus identity index for efficient priority changes and removal.
Combine exact expiry checks with generation-safe cleanup and bounded capacity.
Build a bounded probabilistic membership structure with compatible serialization.
Maintain conflict-free half-open reservations with atomic rescheduling.
Track connected components with path compression, union by size and stable API rules.
Implement exact lookup, prefix enumeration and deletion using compressed edge labels.
Build an ordered map with randomized towers, range scans and injectable randomness.
Construct immutable binary hash trees and verify bounded inclusion proofs.
Implement a fixed-capacity FIFO with wraparound and explicit overflow behavior.
Edit large text using balanced chunk trees with split, join and immutable snapshots.
Build an insertion-only ordered index with leaf splits, separator propagation and range scans.
Find overlapping intervals using an augmented balanced search tree.
Sample immutable integer weights using prefix sums and an injectable unbiased draw source.
Support point updates and ordered half-open range reductions with an associative combine function.
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