Multiple Pattern Matching in LZW Compressed Text

In this paper we address the problem of searching in LZW compressed text directly, and present a new algorithm for finding multiple patterns by simulating the move of the Aho-Corasick pattern matching machine. The new algorithm finds all occurrences of multiple patterns whereas the algorithm proposed by Amir, Benson, and Farach finds only the first occurrence of a single pattern. The new algorithm runs in O(n+m+ r) time using O(n+m) space, where n is the length of the compressed text, m is the length of the total length of the patterns, and r is the number of occurrences of the patterns. We implemented a simple version of the algorithm, and showed that it is approximately twice faster than a decompression followed by a search using the Aho-Corasick machine.