Caching is critical in systems design, from web browsers to database engines. An LRU (Least Recently Used) cache evicts the least recently used entry when full, ensuring hot data stays accessible. Implementing one in code tests your mastery of linked lists, hash maps, and constant-time operations.

Checking for nearby repeated events in a log or sensor stream is a common task in monitoring, fraud detection, and real‑time analytics....

Finding the longest run of consecutive days, IDs, or timestamps in a dataset comes up in analytics, event processing, and scheduling systems. This “Longest Consecutive Sequence” problem is a great way to exercise hashing, set membership, and thinking about how to avoid redundant work.

Finding how many contiguous stretches of transactions sum to a target turns up in budgeting tools, analytics dashboards, and real‑time...

Clustering words that are anagrams of each other is a classic interview problem and mirrors real‑world tasks like building search indexes...