The Roman Domination Number of a Digraph
نویسندگان
چکیده
LetD = (V,A) be a finite and simple digraph. A Roman dominating function (RDF) on a digraph D is a labeling f : V (D) → {0, 1, 2} such that every vertex with label 0 has a in-neighbor with label 2. The weight of an RDF f is the value ω(f) = ∑ v∈V f(v). The Roman domination number of a digraph D, denoted by γR(D), equals the minimum weight of an RDF on D. In this paper we present some sharp bounds for γR(D) 2000 Mathematics Subject Classification: 05C69.
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The Roman domination and domatic numbers of a digraph
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