DictionariesMaps

Dictionariesmaps is a term used in computer science to describe data structures that implement a mapping from keys to values. The name blends the concepts of dictionaries and maps, reflecting how these structures are treated in many programming languages as fundamental containers for key-value associations. In practice, a dictionariesmaps provides operations to insert, update, delete, and look up entries based on a key, and typically supports iteration over stored pairs.

Two primary implementations dominate the landscape: hash-based maps and tree-based maps. Hash-based maps store entries in buckets indexed by a hash of the key, offering average-case constant-time performance for insertions, lookups, and deletions. They generally do not preserve any particular order of keys. Tree-based maps use balanced search trees to maintain keys in a sorted order, delivering O(log n) operation times and ordered iteration. Some languages offer both flavors, sometimes with additional features such as immutability, concurrency guarantees, or customizable eviction policies.

Key requirements usually include that keys be usable as identifiers for equality and, in hash-based variants, hashable. Values can be of arbitrary type. Implementations differ in memory overhead, performance characteristics, and synchronization semantics. Namespaces and type systems in various languages often reflect the same concept with different names, such as dictionary, map, or associative array.

Common uses include symbol tables, configuration stores, caches, and indexes in databases or programming environments. See also associative array, hash table, map, and key-value store.