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Let G be a graph and S ⊆ V (G). For each vertex u ∈ S and for each v ∈ V (G) − S, we define d(u, v) = d(v, u) to be the length of a shortest path in V (G)−(S−{u}) if such a path exists, and ∞ otherwise. Let v ∈ V (G). We define w S (v) = u∈S 1 2 d(u,v)−1 if v ∈ S, and w S (v) = 2 if v ∈ S. If, for each v ∈ V (G), we have w S (v) ≥ 1, then S is an(More)
If G is a connected graph, then the distance between two edges is, by definition, the distance between the corresponding vertices of the line graph of G. The edge-Wiener index W e of G is then equal to the sum of distances between all pairs of edges of G. We give bounds on W e in terms of order and size. In particular we prove the asymptotically sharp upper(More)
For a graph G with weight function w on the vertices, the total distance of G is the sum over all unordered pairs of vertices x and y of w(x)w(y) times the distance between x and y. A MAD tree of G is a spanning tree with minimum total distance. We develop a linear-time algorithm to find a MAD tree of a distance-hereditary graph; that is, those graphs where(More)
Let G = (V, E) be a graph. A set S ⊆ V is a restrained dominating set if every vertex not in S is adjacent to a vertex in S and to a vertex in V \ S. The restrained domination number of G, denoted by γ r (G), is the minimum cardinality of a restrained dominating set of G. A set S ⊆ V is a total dominating set if every vertex in V is adjacent to a vertex in(More)
The eccentricity of a vertex is the maximum distance from it to another vertex and the average eccentricity of a graph is the mean eccentricity of a vertex. In this paper we establish bounds on the mean eccentricity of a graph. We then examine the change in the average eccentricity when a graph is replaced by a spanning subgraph, in particular the two(More)