On partitioning a graph into two connected subgraphs

  • Authors:
  • Daniël Paulusma;Johan M. M. van Rooij

  • Affiliations:
  • Department of Computer Science, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, United Kingdom;Department of Information and Computing Sciences, Universiteit Utrecht, PO Box 80.089, 3508TB Utrecht, The Netherlands

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2011

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Abstract

Suppose a graph G is given with two vertex-disjoint sets of vertices Z"1 and Z"2. Can we partition the remaining vertices of G such that we obtain two connected vertex-disjoint subgraphs of G that contain Z"1 and Z"2, respectively? This problem is known as the 2-Disjoint Connected Subgraphs problem. It is already NP-complete for the class of n-vertex graphs G=(V,E) in which Z"1 and Z"2 each contain a connected set that dominates all vertices in V@?(Z"1@?Z"2). We present an O^*(1.2051^n) time algorithm that solves it for this graph class. As a consequence, we can also solve this problem in O^*(1.2051^n) time for the classes of n-vertex P"6-free graphs and split graphs. This is an improvement upon a recent O^*(1.5790^n) time algorithm for these two classes. Our approach translates the problem to a generalized version of hypergraph 2-coloring and combines inclusion/exclusion with measure and conquer.