Dictionary-symbolwise flexible parsing

  • Authors:

  • Maxime Crochemore;Laura Giambruno;Alessio Langiu;Filippo Mignosi;Antonio Restivo

  • Affiliations:

  • Dept. of Informatics, Kings College London, London WC2R 2LS, UK and Université Paris-Est, Marne-La-Vallée, France;Université Paris 13, Villetaneuse, France and Dip. di Matematica e Informatica, Universití di Palermo, Palermo, Italy;Dip. di Matematica e Informatica, Universití di Palermo, Palermo, Italy and Université Paris-Est, Marne-La-Vallée, France;Dip. di Informatica, Universití dellAquila, LAquila, Italy;Dip. di Matematica e Informatica, Universití di Palermo, Palermo, Italy

  • Venue:
  • Journal of Discrete Algorithms
  • Year:
  • 2012

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Abstract

Linear-time optimal parsing algorithms are rare in the dictionary-based branch of the data compression theory. A recent result is the Flexible Parsing algorithm of Matias and Sahinalp (1999) that works when the dictionary is prefix closed and the encoding of dictionary pointers has a constant cost. We present the Dictionary-Symbolwise Flexible Parsing algorithm that is optimal for prefix-closed dictionaries and any symbolwise compressor under some natural hypothesis. In the case of LZ78-like algorithms with variable costs and any, linear as usual, symbolwise compressor we show how to implement our parsing algorithm in linear time. In the case of LZ77-like dictionaries and any symbolwise compressor our algorithm can be implemented in O(nlogn) time. We further present some experimental results that show the effectiveness of the dictionary-symbolwise approach.