NP-hardness of the recognition of coordinated graphs

A graph G is coordinated if the minimum number of colors that can be assigned to the cliques of H in such a way that no two cliques with non-empty intersection receive the same color is equal to the maximum number of cliques of H with a common vertex, for every induced subgraph H of G. In previous w...

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Autores principales: Soulignac, F.J., Sueiro, G.
Formato: JOUR
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Acceso en línea:http://hdl.handle.net/20.500.12110/paper_02545330_v169_n1_p17_Soulignac
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Sumario:A graph G is coordinated if the minimum number of colors that can be assigned to the cliques of H in such a way that no two cliques with non-empty intersection receive the same color is equal to the maximum number of cliques of H with a common vertex, for every induced subgraph H of G. In previous works, polynomial time algorithms were found for recognizing coordinated graphs within some classes of graphs. In this paper we prove that the recognition problem for coordinated graphs is NP-hard, and it is NP-complete even when restricted to the class of {gem, C 4, odd hole}-free graphs with maximum degree four, maximum clique size three and at most three cliques sharing a common vertex. © 2008 Springer Science+Business Media, LLC.