A note on the total domination number of a tree
نویسندگان
چکیده
A set S of vertices is a total dominating set of a graph G if every vertex of G is adjacent to some vertex in S. The minimum cardinality of a total dominating set is the total domination number t(G). We show that for a nontrivial tree T of order n and with ` leaves, t(T ) > (n+2 `)=2, and we characterize the trees attaining this lower bound. Keywords: total domination, trees. AMS subject classi cation: 05C69
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