yanwii / AhoCorasick

Aho-corasick algorithm for C++/Python.

AhoCorasick

In computer science, the Aho–Corasick algorithm is a string searching algorithm invented by Alfred V. Aho and Margaret J. Corasick. It is a kind of dictionary-matching algorithm that locates elements of a finite set of strings (the "dictionary") within an input text. It's based on a Trie Tree which is a dictonary tree.

Install

pip2 install acer

Use

import acer

ac = acer.Acer()

# add word
ac.add_word("he")   
ac.add_word("she")   
ac.add_word("her")

# then make failure tree
ac.make_ac()

# search
ac.search("ushers")

# insert
ac.insert("his")

NOTICE

After making the failure tree, if you insert a word into trie tree, the failure tree could be imcomplete because the first char of new word could be the failure state of a word which already exist.
Such as:
Add the word "add" first, and then make failure tree
Now insert the "desert", the char "d" in "desert" should have been the failure state of "d" in "add", but it's not work because of the order.

So, after inserting a word, re-making failure tree will be recommended.