Showing papers by "Costas S. Iliopoulos published in 2003"
TL;DR: This paper proposes a data structure called the truncated suffix tree, which is a truncated version of the suffix tree that is particularly a useful data structure for LZ77 that compresses using a sliding window of a fixed size.
57 citations
Proceedings Article•
01 Mar 2003
TL;DR: Two simple practical algorithms that compute all the periods of every prefix of x are presented, which require quadratic worst-case time but only linear time in the average case.
Abstract: We describe algorithms for computing typical regularities in strings x = x[1n] that contain don't care symbols For such strings on alphabet Σ, an O(n log n log |Σ|) worst-case time algorithm for computing the period is known, but the algorithm is impractical due to a large constant of proportionality We present instead two simple practical algorithms that compute all the periods of every prefix of x; our algorithms require quadratic worst-case time but only linear time in the average case We then show how our algorithms can be used to compute other string regularities, specifically the covers of both ordinary and circular strings
41 citations
Proceedings Article•
01 Jan 2003
TL;DR: It is proved that the minimum k-cover problem is in fact NP-hard and two greedy algorithms are proposed that are implemented and tested on different kind of data.
Abstract: We study the minimum k-cover problem. For a given string x of length n and an integer k, the minimum k-cover is the minimum set of k-substrings that covers x. We show that the on-line algorithm that has been proposed by Iliopoulos and Smyth [IS92] is not correct. We prove that the problem is in fact NP-hard. Furthermore, we propose two greedy algorithms that are implemented and tested on different kind of data.
15 citations
01 Jan 2003
15 citations
TL;DR: It is shown that the δ-matching is reducible to k instances of pattern- matching with don't cares, and how the numbers δ and k are related by introducingδ-distinguishing families H of morphisms is investigated.
14 citations
Proceedings Article•
01 Jan 2003
TL;DR: In this paper, the smallest distance approximate seed problem is solved in polynomial time under a variety of distance rules (the Hamming distance, the edit distance, and the weighted edit distance).
Abstract: In this paper we study approximate seeds of strings, that is, substrings of a given string x that cover (by concatenations or overlaps) a superstring of x, under a variety of distance rules (the Hamming distance, the edit distance, and the weighted edit distance). We solve the smallest distance approximate seed problem and the restricted smallest approximate seed problem in polynomial time and we prove that the general smallest approximate seed problem is NP-complete.
13 citations
08 Oct 2003
TL;DR: This is the first character-skipping algorithm that skips characters using both δ and γ, and results on real music showing that the algorithm is superior to current alternatives.
Abstract: (δ,γ)-Matching is a string matching problem with applications to music retrieval. The goal is, given a pattern P 1... m and a text T 1... n on an alphabet of integers, find the occurrences P′ of the pattern in the text such that (i) ∀ 1 ≤ i ≤ m, |P i − P′ i | ≤ δ, and (ii) ∑ 1 ≤ i ≤ m |P i − P′ i | ≤ γ. Several techniques for (δ,γ)-matching have been proposed. In this paper we show that a classical string matching technique that combines bit-parallelism and suffix automata can be successfully adapted to this problem. This is the first character-skipping algorithm that skips characters using both δ and γ. We implemented our algorithm and drew experimental results on real music showing that our algorithm is superior to current alternatives.
12 citations
Proceedings Article•
01 Jan 2003
10 citations
Journal Article•
TL;DR: This is the first character-skipping algorithm that skips characters using both δ and γ, and results on real music showing that the algorithm is superior to current alternatives.
Abstract: (δ,γ)-Matching is a string matching problem with applications to music retrieval. The goal is, given a pattern P 1...m and a text T 1...n on an alphabet of integers, find the occurrences P' of the pattern in the text such that (i) ∀1 < i < m, |P i - P' i | < δ, and (ii) Σ1
12 Sep 2003
TL;DR: This paper implements algorithms for solving the smallest distance approximate period/cover/seed problem and the restricted smallest approximate period-cover-seed problem in polynomial time, under a variety of distance rules (the Hamming distance, the edit distance, and the weighted edit distance).
Abstract: In this paper we study approximate regularities of strings, that is, approximate periods, approximate covers and approximate seeds. We explore their similarities and differences and we implement algorithms for solving the smallest distance approximate period/cover/seed problem and the restricted smallest approximate period/cover/seed problem in polynomial time, under a variety of distance rules (the Hamming distance, the edit distance, and the weighted edit distance). We then analyse our experimental results to find out the time complexity of the algorithms in practice.