Maximization Coloring Problems on graphs with few P4s

Description

Given a graph G = (V;E), a greedy coloring of G is a proper coloring such that, for each two colors i < j, every vertex of V(G) colored j has a neighbor with color i. The greatest k such that G has a greedy coloring with k colors is the Grundy number of G. A b-coloring of G is a proper coloring such that every color class contains a vertex which is adjacent to at least one vertex in every other color class. The greatest integer k for which there exists a b-coloring of G with k colors is its b-chromatic number. Determining the Grundy number and the b-chromatic number of a graph are NP-hard problems in general. For a fixed q, the (q;q-4)-graphs are the graphs for which no set of at most q vertices induces more than q-4 distinct induced P4s. In this paper, we obtain polynomial-time algorithms to determine the Grundy number and the b-chromatic number of (q;q-4)-graphs, for a fixed q. They generalize previous results obtained for cographs and P4-sparse graphs, classes strictly contained in the (q;q-4)-graphs.

Abstract

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