Improved Circular Dictionary Matching

Abstract

The circular dictionary matching problem is an extension of the classical dictionary matching problem where every string in the dictionary is interpreted as a circular string: after reading the last character of a string, we can move back to its first character. The circular dictionary matching problem is motivated by applications in bioinformatics and computational geometry. In 2011, Hon et al. [ISAAC 2011] showed how to efficiently solve circular dictionary matching queries within compressed space by building on Mantaci et al.'s eBWT and Sadakane's compressed suffix tree. The proposed solution is based on the assumption that the strings in the dictionary are all distinct and non-periodic, no string is a circular rotation of some other string, and the strings in the dictionary have similar lengths. In this paper, we consider arbitrary dictionaries, and we show how to solve circular dictionary matching queries in $ O((m + occ) \log n) $ time within compressed space using $ n \log \sigma (1 + o(1)) + O(n) + O(d \log n) $ bits, where $ n $ is the total length of the dictionary, $ m $ is the length of the pattern, $ occ $ is the number of occurrences, $ d $ is the number of strings in the dictionary and $ \sigma $ is the size of the alphabet. Our solution is based on an extension of the suffix array to arbitrary dictionaries and a sampling mechanism for the LCP array of a dictionary inspired by recent results in graph indexing and compression.