A subexponential algorithm for the coloured tree partition problem

  • Authors:
  • Roberto Cordone

  • Affiliations:
  • Dipartimento di Tecnologie dell'Informazione, Universití degli Studi di Milano, Via Bramante 65, 26013 - Crema, Italy

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2007

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Abstract

Given a tree of n vertices and a list of feasible colours for each vertex, the coloured tree partition problem (CTPP) consists in partitioning the tree into p vertex-disjoint subtrees of minimum total cost, and assigning to each subtree a different colour, which must be feasible for all of its vertices. The problem is strongly NP-hard on general graphs, as well as on grid and bipartite graphs. This paper deals with the previously open case of tree graphs, showing that it is strongly NP-complete to determine whether a feasible solution exists. It presents reduction, decomposition and bounding procedures to simplify the problem and an exact algorithm of O(np^l^o^g^"^2^(^a^p^-^2^)) complexity (with a32) for the special case in which a vertex of each subtree is given.