Solving the String Statistics Problem in Time O(n log n)

  • Authors:
  • Gerth Stølting Brodal;Rune B. Lyngsø;Anna Östlin;Christian N. S. Pedersen

  • Affiliations:
  • -;-;-;-

  • Venue:
  • ICALP '02 Proceedings of the 29th International Colloquium on Automata, Languages and Programming
  • Year:
  • 2002

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Abstract

The stringstatistics problem consists of preprocessinga stringof length n such that given a query pattern of length m, the maximum number of non-overlappingo ccurrences of the query pattern in the stringcan be reported efficiently. Apostolico and Preparata introduced the minimal augmented suffix tree (MAST) as a data structure for the stringstatistics problem, and showed how to construct the MAST in time O(n log2 n) and how it supports queries in time O(m) for constant sized alphabets. A subsequent theorem by Fraenkel and Simpson stating that a stringhas at most a linear number of distinct squares implies that the MAST requires space O(n). In this paper we improve the construction time for the MAST to O(n log n) by extendingthe algorithm of Apostolico and Preparata to exploit properties of efficient joining and splitting of search trees together with a refined analysis.