In a graph G, an efficient dominating set is a subset D of vertices such that D is an independent set and each vertex outside D has exactly one neighbor in D. The Minimum Weight Efficient Dominating Set (Min-WED) problem asks for an efficient dominating set of total minimum weight in a given vertex-weighted graph; the Maximum Weight Efficient Dominating Set (Max-WED) problem is defined similarl...

We present an O∗(1.0836n)-time algorithm for finding a maximum independent set in an n-vertex graph with degree bounded by 3, which improves all previous running time bounds for this problem. Our approach has the following two features. Without increasing the number of reduction/branching rules to get an improved time bound, we first successfully extract the essence from the previously known re...

Given a graph G = (V,E) and a (not necessarily proper) edgecoloring of G, we consider the complexity of finding a spanning tree of G with as many different colors as possible, and of finding one with as few different colors as possible. We show that the first problem is equivalent to finding a common independent set of maximum cardinality in two matroids, implying that there is a polynomial alg...

In the token jumping problem for a vertex subset problem Q on graphs we are given a graph G and two feasible solutions Ss, St ⊆ V (G) of Q with |Ss| = |St|, and imagine that a token is placed on each vertex of Ss. The problem is to determine whether there exists a sequence S1, . . . , Sn of feasible solutions, where S1 = Ss, Sn = St and each Si+1 results from Si, 1 ≤ i < n, by moving exactly on...

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...

A k-dominating set of a graph G is a set S of vertices of G such that every vertex outside of S has k neighbors in S. The k-domination number of G, written γk(G), is the size of the smallest k-dominating set in G. In this paper, we derive sharp upper and lower bounds on γk(G) + γk(G) and γk(G)γk(G), where G is the complement of G. We use the results for k = 2 to prove a conjecture of Alon, Balo...

Motivation Want to learn a combinatorial parameter of a graph: the maximum matching size the independence number α(G), the minimum vertex cover size, the minimum dominating set size Krzysztof Onak – Sublinear Graph Approximation Algorithms – p. 2/32 Motivation Want to learn a combinatorial parameter of a graph: the maximum matching size the independence number α(G), the minimum vertex cover siz...

Let G be a graph. A set S of vertices of G is called a total dominating set of G if every vertex of G is adjacent to at least one vertex in S. The total domination number γt(G) and the matching number α ′(G) of G are the cardinalities of the minimum total dominating set and the maximum matching of G, respectively. In this paper, we will introduce an upper bound of the difference between γt(G) a...