The wide window string matching algorithm

  • Authors:

  • Longtao He;Binxing Fang;Jie Sui

  • Affiliations:

  • Research Center of Computer Network and Information Security Technology, Harbin Institute of Technology, Harbin, PR China;Research Center of Computer Network and Information Security Technology, Harbin Institute of Technology, Harbin, PR China;Graduate School of the Chinese Academy of Sciences, Beijing, PR China

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2005

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Abstract

Generally, current string matching algorithms make use of a window whose size is equal to pattern length. In this paper, we present a novel string matching algorithm named WW (for Wide Window) algorithm, which divides the text into [n/m] overlapping windows of size 2m - 1. In the windows, the algorithm attempts m possible occurrence positions in parallel. It firstly searches pattern suffixes from middle to right with a forward suffix automaton, shifts the window directly when it fails, otherwise, scans the corresponding prefixes backward with a reverse prefix automaton. Theoretical analysis shows that WW has optimal time complexity of O(n) in the worst, O(n/m) best and O(n(logσm)/m) for average case. Experimental comparison of WW with existing algorithms validates our theoretical claims for searching long patterns. It further reveals that WW is also efficient for searching short patterns.