Vertex insertion approximates the crossing number of apex graphs

  • Authors:
  • Markus Chimani;Petr Hlinný;Petra Mutzel

  • Affiliations:
  • Faculty of Mathematics and Computer Science, Friedrich-Schiller-University Jena, Ernst-Abbe-Platz 2, 07743 Jena, Germany;Faculty of Informatics, Masaryk University, Brno, Botanická 68a, 60200 Brno, Czech Republic;Faculty of Computer Science, TU Dortmund, Otto-Hahn-Str. 14, 44227 Dortmund, Germany

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2012

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Abstract

An apex graph is a graph G from which only one vertex v has to be removed to make it planar. We show that the crossing number of such G can be approximated up to a factor of @D(G-v)@?d(v)/2 by solving the vertex inserting problem, i.e. inserting a vertex plus incident edges into an optimally chosen planar embedding of a planar graph. Since the latter problem can be solved in polynomial time, this establishes the first polynomial fixed-factor approximation algorithm for the crossing number problem of apex graphs with bounded degree. Furthermore, we extend this result by showing that the optimal solution for inserting multiple edges or vertices into a planar graph also approximates the crossing number of the resulting graph.