Setint

Setint is a data structure designed to store a collection of integers with two defining properties: elements are unique and order is not guaranteed (in hash-based implementations) or defined (in ordered implementations). It provides fast membership testing and supports standard set operations. The term setint is often used as a generic identifier for a set whose elements are integers, rather than a language-specific type.

Common implementations include hash sets and balanced binary search trees. Hash sets provide near-constant time insertion and lookup on average, while tree-based sets preserve element order and offer O(log n) operations. Some implementations use bit-level representations when the range of integers is limited, trading memory for faster membership tests.

Typical operations include add and remove, contains, size, and iterators. Additional operations include is_subset, union, intersection, and difference. Performance depends on the underlying structure and quality of the hash function or tree balancing; worst-case operations in hash sets can degrade to linear time under collisions, while tree-based sets offer guaranteed logarithmic time.

Use cases include de-duplication, fast membership checks in algorithms, and problems involving finite sets of integers. In programming languages, examples include Python’s built-in set, C++'s unordered_set<int> (or set<int> for an ordered variant), Java’s HashSet<Integer>, and Rust’s HashSet<i32>. For dense ranges, a bitset may be a more memory-efficient alternative, and for small sets, a sorted vector with binary search can be efficient.

See also: Set, Hash set, Bitset, Integer set.