Hash Set
A hash set is a data structure that stores unique elements using a hash table, providing average constant-time complexity for insertion, deletion, and lookup operations. It is implemented by hashing elements to indices in an underlying array and handling collisions through techniques like chaining or open addressing. Hash sets are commonly used for fast membership testing and duplicate removal in collections.
Developers should use hash sets when they need efficient O(1) average-time operations for checking if an element exists, adding new unique items, or removing duplicates from datasets. They are ideal for applications like caching, spell-checking, graph algorithms (e.g., visited node tracking), and data deduplication in large-scale systems where performance is critical.