Finding one tight cycle

  • Authors:
  • Sergio Cabello;Matt DeVos;Jeff Erickson;Bojan Mohar

  • Affiliations:
  • IMFM, and FMF, University of Ljubljana, Slovenia;Simon Fraser University, Burnaby, B.C.;University of Illinois at Urbana-Champaign;Simon Fraser University, and IMFM

  • Venue:
  • Proceedings of the nineteenth annual ACM-SIAM symposium on Discrete algorithms
  • Year:
  • 2008

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Abstract

A cycle on a combinatorial surface is tight if it as short as possible in its (free) homotopy class. We describe an algorithm to compute a single tight, non-contractible, simple cycle on a given orientable combinatorial surface in O(n log n) time. The only method previously known for this problem was to compute the globally shortest non-contractible or non-separating cycle in O(min{g3, n} n log n) time, where g is the genus of the surface. As a consequence, we can compute the shortest cycle freely homotopic to a chosen boundary cycle in O(n log n) time and a tight octagonal decomposition in O(gn log n) time.