Abstract
The Grundy number of a graph G, denoted by Γ(G), is the largest k such that G has a greedy k-colouring, that is a colouring with k colours obtained by applying the greedy algorithm according to some ordering of the vertexes of G. The b-chromatic number of a graph G, denoted by χ b (G), is the largest k such that G has a b-colouring with k colours, that is a colouring in which each colour class contains a b-vertex, a vertex with neighbours in all other colour classes. Trivially χ b (G),Γ(G)≤Δ(G)+1. In this paper, we show that deciding if Γ(G)≤Δ(G) is NP-complete even for a bipartite graph G. We then show that deciding if Γ(G)≥|V(G)|−k or if χ b (G)≥|V(G)|−k are fixed parameter tractable problems with respect to the parameter k.
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F. Havet was partially supported by ANR Blanc AGAPE, ANR-09-BLAN-0159.
L. Sampaio was partially supported by CAPES/Brazil and ANR Blanc AGAPE, ANR-09-BLAN-0159.
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Havet, F., Sampaio, L. On the Grundy and b-Chromatic Numbers of a Graph. Algorithmica 65, 885–899 (2013). https://doi.org/10.1007/s00453-011-9604-4
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DOI: https://doi.org/10.1007/s00453-011-9604-4