MSOL restricted contractibility to planar graphs

  • Authors:
  • James Abello;Pavel Klavík;Jan Kratochvíl;Tomáš Vyskočil

  • Affiliations:
  • DIMACS Center for Discrete Mathematics and Theorethical Computer Science, Rutgers University, Piscataway, NJ;Department of Applied Mathematics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic;Department of Applied Mathematics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic;Department of Applied Mathematics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic

  • Venue:
  • IPEC'12 Proceedings of the 7th international conference on Parameterized and Exact Computation
  • Year:
  • 2012

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Abstract

We study the computational complexity of graph planarization via edge contraction. The problem Contract asks whether there exists a set S of at most k edges that when contracted produces a planar graph. We give an FPT algorithm in time $\mathcal{O}(n^2 f(k))$ which solves a more general problem P-RestrictedContract in which S has to satisfy in addition a fixed inclusion-closed MSOL formula P. For different formulas P we get different problems. As a specific example, we study the ℓ-subgraph contractability problem in which edges of a set S are required to form disjoint connected subgraphs of size at most ℓ. This problem can be solved in time $\mathcal{O}(n^2 f'(k,l))$ using the general algorithm. We also show that for ℓ≥2 the problem is NP-complete. And it remains NP-complete when generalized for a fixed genus (instead of planar graphs).