Hashset
A hash set is a collection of distinct values that uses hashing to support efficient membership testing without associated values.
Fabulous Adventures in Data Structures and Algorithms
HashSet<T> is a .NET collection type that stores unique values and supports hash-based membership and lookup operations.
- How it is used
- Supports fast word-membership tests while serving as a rejected alternative for prefix-oriented word-list searches.
- How deep it goes
- Explains hashing, buckets, complexity, equality contracts, and mutation hazards, but stops short of implementing the collection itself.
- Examples
- Uses large word lists, Contains, StartsWith, and structurally equivalent mutable graph nodes as examples.
- What you can do after
- Evaluate hash sets for membership workloads and implement compatible equality and hashing for stored objects.
Read how Fabulous Adventures in Data Structures and Algorithms explains hashset →
Kotlin in Action, 2E
HashSet is a set implementation that organizes elements using hash codes for efficient membership testing.
- How it is used
- Uses hash codes to implement set membership checks, especially when storing objects with value-based equality.
- How deep it goes
- Explains hash-first comparison and the equals/hashCode contract, then stops short of implementation internals beyond a hashCode example.
- Examples
- Uses two equal-looking Customer instances named Alice and compares Kotlin hashSetOf with java.util.HashSet interoperability.
- What you can do after
- Diagnose membership failures by checking whether equal objects return the same hash code.
Related concepts
- equality by valueuses · Equality by value is an equality semantics in which values are considered equal when they represent equivalent contents, regardless of object identity.
- hash valueuses · A hash value is a deterministic, typically fixed-size value produced by applying a hash function to input data, often for lookup, comparison, identification, or integrity checking.
- Mapkind of · A map is an associative data structure that stores key-value pairs and supports retrieving values by key.
- setused by · A set is a collection of unique elements in which membership is determined by whether an element is present, not by duplicate occurrences.
- bloom filteralternative to · A Bloom filter is a space-efficient probabilistic data structure for testing set membership that permits false positives but not false negatives.
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