In computer science, an associative array, map, or dictionary is an abstract data type composed of a collection of (key, value) pairs, such that each possible key appears at most once in the collection.
Operations associated with this data type allow:
- the addition of pairs to the collection
- the removal of pairs from the collection
- the modification of the values of existing pairs
- the lookup of the value associated with a particular key
The dictionary problem is the task of designing a data structure that implements an associative array. A standard solution to the dictionary problem is a hash table; in some cases it is also possible to solve the problem using directly addressed arrays, binary search trees, or other more specialized structures.
Many programming languages include associative arrays as primitive data types, and they are available in software libraries for many others. Content-addressable memory is a form of direct hardware-level support for associative arrays.
Associative arrays have many applications including such fundamental programming patterns as memoization and the decorator pattern.
Read more about Associative Array: Operations, Example, Implementation, Language Support
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