May 26, 2018

Data structure optimized for prefix lookup

This module implements a trie data structure. The term “trie” comes from the word retrieval, but is generally pronounced like “try”. A trie is a tree structure or directed acyclic graph, the nodes of which represent letters in a word. For example, the final lookup for the word ‘bob’ would look something like $ref->’b’‘o’‘b’‘00’ the 00 being an end marker. Only nodes which would represent words in the trie exist, making the structure slightly smaller than a hash of the same data set.

The advantages of the trie over other data storage methods is that lookup times are O1 WRT the size of the index. For sparse data sets, it is probably not as efficient as performing a binary search on a sorted list, and for small files, it has a lot of overhead. The main advantage at least from my perspective is that it provides a relatively cheap method for finding a list of words in a large, dense data set which begin with a certain string.

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