Counting H-Colorings of Partial k-Trees

  • Authors:
  • Josep Díaz;Maria J. Serna;Dimitrios M. Thilikos

  • Affiliations:
  • -;-;-

  • Venue:
  • COCOON '01 Proceedings of the 7th Annual International Conference on Computing and Combinatorics
  • Year:
  • 2001

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Abstract

The problem of counting all H-colorings of a graph G of n vertices is considered. While the problem is, in general, #P-complete, we give linear time algorithms that solve the main variants of this problem when the input graph G is a k-tree or, in the case where G is directed, when the underlying graph of G is a k-tree. Our algorithms remain polynomial even in the case where k = O(log n) or in the case where the size of H is O(n). Our results are easy to implement and imply the existence of polynomial time algorithms for a series of problems on partial k-trees such as core checking and chromatic polynomial computation.