Core Data Structures Questions

Fundamental built-in data structures used in everyday programming and coding interviews: arrays/lists, strings, and hash maps (dictionaries). For array-like sequences, cover indexing, slicing or sub-ranging, iteration, common mutation operations (appending, inserting, removing elements), common algorithms such as sorting and reversing, and the memory and performance implications of each. For strings, cover indexing, slicing or substring extraction, common operations such as splitting, joining, trimming, and replacing, and general approaches to string manipulation and pattern processing. For hash maps and dictionaries, cover key value semantics, insertion and lookup, iteration patterns, safe access idioms (defaults, existence checks), and using hash tables for counting and grouping. Candidates should know the time complexity of common operations in plain terms (constant time, linear time, quadratic time) and be able to choose the appropriate structure for a problem and reason about space and performance tradeoffs. Practice should include implementation level manipulation exercises and classic interview problems such as two sum and frequency counting, written clearly in whatever language the candidate is most comfortable with (a specific language may be used for concrete code examples without the underlying concept being tied to it).