Finding shortest non-separating and non-contractible cycles for topologically embedded graphs

  • Authors:
  • Sergio Cabello;Bojan Mohar

  • Affiliations:
  • Department of Mathematics, Institute for Mathematics, Physics and Mechanics, Slovenia;Department of Mathematics, Faculty of Mathematics and Physics, University of Ljubljana, Slovenia

  • Venue:
  • ESA'05 Proceedings of the 13th annual European conference on Algorithms
  • Year:
  • 2005

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Abstract

We present an algorithm for finding shortest surface non-separating cycles in graphs with given edge-lengths that are embedded on surfaces. The time complexity is O(g3/2V3/2log V+g5/2V1/2), where V is the number of vertices in the graph and g is the genus of the surface. If g=o(V1/3−ε), this represents a considerable improvement over previous results by Thomassen, and Erickson and Har-Peled. We also give algorithms to find a shortest non-contractible cycle in O(g$^{O({\it g})}$V3/2) time, improving previous results for fixed genus. This result can be applied for computing the (non-separating) face-width of embedded graphs. Using similar ideas we provide the first near-linear running time algorithm for computing the face-width of a graph embedded on the projective plane, and an algorithm to find the face-width of embedded toroidal graphs in O(V5/4log V) time.