Complexity issues for the sandwich homogeneous set problem

  • Authors:
  • Arnaud Durand;Michel Habib

  • Affiliations:
  • íquipe de logique mathématique, FRE 3233 CNRS & Universitéé Paris Diderot Paris 7, UFR de Mathématiques - case 7012, site Chevaleret, 75205 Paris Cedex 13, France;LIAFA, UMR 7089 CNRS & Universitéé Paris Diderot - Paris 7, UFR d'Informatique - case 7014, F-75205 Paris Cedex 13, France

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2011

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Abstract

Graph sandwich problems were introduced by Golumbic et al. (1994) in [12] for DNA physical mapping problems and can be described as follows. Given a property @P of graphs and two disjoint sets of edges E"1, E"2 with E"1@?E"2 on a vertex set V, the problem is to find a graph G on V with edge set E"s having property @P and such that E"1@?E"s@?E"2. In this paper, we exhibit a quasi-linear reduction between the problem of finding an independent set of size k=2 in a graph and the problem of finding a sandwich homogeneous set of the same size k. Using this reduction, we prove that a number of natural (decision and counting) problems related to sandwich homogeneous sets are hard in general. We then exploit a little further the reduction and show that finding efficient algorithms to compute small sandwich homogeneous sets would imply substantial improvement for computing triangles in graphs.