On-line coloring of h-free bipartite graphs

  • Authors:
  • H. J. Broersma;A. Capponi;D. Paulusma

  • Affiliations:
  • Department of Computer Science, Durham University, Durham, England;Computer Science, Division of Engineering and Applied Sciences, California Institute of Technology;Department of Computer Science, Durham University, Durham, England

  • Venue:
  • CIAC'06 Proceedings of the 6th Italian conference on Algorithms and Complexity
  • Year:
  • 2006

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Abstract

We present a new on-line algorithm for coloring bipartite graphs. This yields a new upper bound on the on-line chromatic number of bipartite graphs, improving a bound due to Lovász, Saks and Trotter. The algorithm is on-line competitive on various classes of H – free bipartite graphs, in particular P6-free bipartite graphs and P7-free bipartite graphs, i.e., that do not contain an induced path on six, respectively seven vertices. The number of colors used by the on-line algorithm in these particular cases is bounded by roughly twice, respectively roughly eight times the on-line chromatic number. In contrast, it is known that there exists no competitive on-line algorithm to color P6-free (or P7-free) bipartite graphs, i.e., for which the number of colors is bounded by any function only depending on the chromatic number.