PSC2019

Wed, 28 Aug 2019 00:00:00 +0000

In this paper, we propose a new pattern matching algorithm based on the Franek-Jennings-Smyth (FJS) algorithm. The FJS algorithm is a hybrid of the Knuth-Morris-Pratt (KMP) and the Sunday algorithms. The worst case time complexity of the KMP algorithm is linear time and the Sunday algorithm is quadratic time. However, the Sunday algorithm is faster than the KMP algorithm in practice. Inheriting the virtues of those algorithms, the FJS algorithm runs in linear time in the worst case and fast in practice. We improve the FJS algorithm by further taking an idea inspired by the Quite-Naive algorithm by Cantone and Faro. The experimental results show that our algorithm is faster than the FJS algorithm in general except when a pattern is extremely short.

PSC2016

Mon, 29 Aug 2016 00:00:00 +0000

A multi-track string is a tuple of strings of the same length. The full permuted pattern matching problem is, given two multi-track strings $\mathcal{T} = (t_1, t_2,\ldots, t_N)$ and $\mathcal{P} = (p_1, p_2,\ldots, p_N)$ such that $|p_1|= \cdots =|p_N| \leq |t_1| = \ldots =|t_N|$, to find all positions $i$ such that $\mathcal{P} = (t_{r_1}[i:i+m-1], \ldots, t_{r_N}[i:i+m-1])$ for some permutation $(r_1, \ldots, r_N)$ of $(1, \ldots, N)$, where $m=|p_1|$ and $t[i:j]$ denotes the substring of t from position $i$ to $j$. We propose new algorithms that perform full permuted pattern matching practically fast. The first and second algorithms are based on the Boyer-Moore algorithm and the Horspool algorithm, respectively. The third algorithm is based on the Aho-Corasick algorithm where we use a multi-track character instead of a single character in the so-called goto function. The fourth algorithm is an improvement of the multi-track Knuth-Morris-Pratt algorithm that uses an automaton instead of the failure function of the original algorithm. Our experiment results demonstrate that those algorithms perform permuted pattern matching faster than existing algorithms.

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