Finding a long directed cycle

  • Authors:
  • Harold N. Gabow;Shuxin Nie

  • Affiliations:
  • University of Colorado at Boulder, Boulder, CO;University of Colorado at Boulder, Boulder, CO

  • Venue:
  • ACM Transactions on Algorithms (TALG)
  • Year:
  • 2008

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Abstract

Consider a digraph with n vertices. For any fixed value k, we present linear- and almost-linear-time algorithms to find a cycle of length ≥ k, if one exists. We also find a cycle that has length ≥ log n/log log n in polynomial time, if one exists. Under an appropriate complexity assumption it is known to be impossible to improve this guarantee by more than a log log n factor. Our approach is based on depth-first search.