Hash tree (persistent data structure)

In computer science, a hash tree (or hash trie) is a persistent data structure that can be used to implement sets and maps, intended to replace hash tables in purely functional programming. In its basic form, a hash tree stores the hashes of its keys, regarded as strings of bits, in a trie, with the actual keys and (optional) values stored at the trie's "final" nodes.^[1]

Hash array mapped tries and Ctries are refined versions of this data structure, using particular type of trie implementations.^[1]