Approximating the minimum clique cover and other hard problems in subtree filament graphs

  • Authors:
  • J. Mark Keil;Lorna Stewart

  • Affiliations:
  • Department of Computer Science University of Saskatchewan, Saskatoon, Saskatchewan, Canada;Department of Computing Science, University of Alberta, Edmonton, Alberta, Canada

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2006

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Abstract

Subtree filament graphs are the intersection graphs of subtree filaments in a tree. This class of graphs contains subtree overlap graphs, interval filament graphs, chordal graphs, circle graphs, circular-arc graphs, cocomparability graphs, and polygon-circle graphs. In this paper we show that, for circle graphs, the clique cover problem is NP-complete and the h-clique cover problem for fixed h is solvable in polynomial time. We then present a general scheme for developing approximation algorithms for subtree filament graphs, and give approximation algorithms developed from the scheme for the following problems which are NP-complete on circle graphs and therefore on subtree filament graphs: clique cover, vertex colouring, maximum k-colourable subgraph, and maximum h-coverable subgraph.