On the number of plane graphs

  • Authors:
  • Oswin Aichholzer;Thomas Hackl;Birgit Vogtenhuber;Clemens Huemer;Ferran Hurtado;Hannes Krasser

  • Affiliations:
  • Graz University of Technology, Graz, Austria;Graz University of Technology, Graz, Austria;Graz University of Technology, Graz, Austria;Universitat Politècnica de Catalunya, Barcelona, Spain;Universitat Politècnica de Catalunya, Barcelona, Spain;Graz University of Technology, Graz, Austria

  • Venue:
  • SODA '06 Proceedings of the seventeenth annual ACM-SIAM symposium on Discrete algorithm
  • Year:
  • 2006

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Abstract

We investigate the number of plane geometric, i.e., straight-line, graphs, a set S of n points in the plane admits. We show that the number of plane graphs and connected plane graphs as well as the number of cycle-free plane graphs is minimized when S is in convex position. Moreover, these results hold for all these graphs with an arbitrary but fixed number of edges. Consequently, we provide simple proofs that the number of spanning trees, cycle-free graphs (forests), perfect matchings, and spanning paths is also minimized for point sets in convex position.In addition we construct a new extremal configuration, the so-called double zig-zag chain. Most noteworthy this example bears Θ*(√72n) = Θ*(8.4853n) triangulations and Θ*(41.1889n) plane graphs (omitting polynomial factors in both cases), improving the previously known best maximizing examples.