Hash Maps and Sets Questions

Understanding how hash based key value stores and set data structures are used to implement fast membership tests, frequency counting, grouping, deduplication, caching, and memoization. Candidates should be able to explain average constant time insert and lookup behavior, discuss collision handling and memory overhead, and compare trade offs with alternative approaches such as sorting, balanced trees, arrays, or bit sets. Expect applied examples such as two sum, sliding window frequency maps, top K counting, union and intersection operations, and discussions of time versus space trade offs when selecting a structure.