The structure of subword graphs and suffix trees of Fibonacci words

  • Authors:
  • Wojciech Rytter

  • Affiliations:
  • Institute of Informatics, Warsaw University, Warsaw, Poland

  • Venue:
  • Theoretical Computer Science - Implementation and application of automata
  • Year:
  • 2006

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Abstract

We use automata-theoretic approach to analyze properties of Fibonacci words. The directed acyclic subword graph (dawg) is a useful deterministic automaton accepting all suffixes of the word. We show that dawg's of Fibonacci words have particularly simple structure. Our main result is a unifying framework for a large collection of relatively simple properties of Fibonacci words. The simple structure of dawgs of Fibonacci words gives in many cases simplified alternative proofs and new interpretation of several well-known properties of Fibonacci words. In particular, the structure of lengths of paths corresponds to a number-theoretic characterization of occurrences of any subword. Using the structural properties of dawg's it can be easily shown that for a string ω we can check if ω is a subword of a Fibonacci word in time O(|ω|) and O(1) space. Compact dawg's of Fibonacci words show a very regular structure of their suffix trees and show how the suffix tree for the Fibonacci word grows (extending the leaves in a very simple way) into the suffix tree for the next Fibonacci word.