The Vertex-Edge Locating Roman Domination of Some Graphs

Abstract

In this paper, we introduce the concept of vertex-edge locating Roman dominating functions in graphs. A vertex-edge locating Roman dominating (\(ve-LRD\)) function of a graph \(G=(V,E)\) is a function \(f:V(G)\rightarrow\{0,1,2\}\) such that the following conditions are satisfied: (i) for every adjacent vertices \(u,v\) with \(f(u)=0\) or \(f(v)=0\), there exists a vertex \(w\) at distance \(1\) or \(2\) from \(u\) or \(v\) with \(f(w)=2\), (ii) for every edge \(uv\in E\), \(max[f(u),f(v)]\neq 0\) and (iii) any pair of distinct vertices \(u,v\) with \(f(u)=f(v)=0\) does not have a common neighbour \(w\) with \(f(w)=2\) . The weight of \(ve\)-LRD function is the sum of its function values over all the vertices. The vertex-edge locating Roman domination number of \(G\) denoted by \(\gamma_{ve-LR}^P(G)\) is the minimum weight of a \(ve\)-LRD function in \(G\). We proved that the vertex-edge locating Roman domination problem is NP complete for bipartite graphs. Also, we present the upper and lower bonds of \(ve\)-LRD function for trees. Lastly, we give the upper bounds of \(ve\)-LRD function for some connected graphs.