Abstract
A Roman dominating function (RDF) of a graph G is a labeling \(f:V(G)\longrightarrow \{0,1,2\}\) such that every vertex with label 0 has a neighbor with label 2. The weight of an RDF is the sum of its functions values over all vertices, and the Roman domination number of G is the minimum weight of an RDF of G. The Roman domination subdivision number \(\mathrm {sd}_{\gamma _{R}}(G)\) is the minimum number of edges that must be subdivided (each edge in G can be subdivided at most once) in order to increase the Roman domination number of G. In this paper, we present a new upper bound on the Roman domination subdivision number by showing that for every connected graph G of order at least three,
where \(\deg _2(v)\) is the number of vertices of G at distance 2 from vertex v. Moreover, we show that the decision problem associated with \(\mathrm {sd}_{\gamma _{R}}(G)\) is NP-hard for bipartite graphs.
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Acknowledgements
This work was supported by the National Key R & D Program of China (Grant No. 2019YFA0706402) and the Natural Science Foundation of Guangdong Province under grant 2018A0303130115.
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Amjadi, J., Khoeilar, R., Chellali, M. et al. On the Roman domination subdivision number of a graph. J Comb Optim 40, 501–511 (2020). https://doi.org/10.1007/s10878-020-00597-x
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DOI: https://doi.org/10.1007/s10878-020-00597-x