In computer science and software engineering, a Judy array is a data structure that has high performance, low memory usage and implements an associative array. Unlike normal arrays, Judy arrays may be sparse, that is, they may have large ranges of unassigned indices. They can be used for storing and looking up values using integer or string keys. The key benefits of using Judy is its scalability, high performance, memory efficiency and ease of use.
Judy arrays are both speed- and memory-efficient, with no tuning or configuration required and therefore they can replace common data structures (skip lists, linked lists, binary, ternary, b-trees, hashing) and work better with very large data sets.
Roughly speaking, it is similar to a highly-optimised 256-ary trie data structure. To make memory consumption small, Judy arrays use over 20 different compression techniques to compress trie nodes.
The Judy array was invented by Douglas Baskins and named after his sister.
Read more about Judy Array: Terminology, Drawbacks
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