The Reversing Number of a Digraph; A Disjoint Union of Directed Stars
نویسنده
چکیده
A minimum feedback arc set of a digraph is a smallest sized set of arcs that when reversed makes the resulting digraph acyclic. Given an acyclic digraph D, we seek a smallest sized tournament T that has D as a minimum feedback arc set. The reversing number of a digraph was defined by Barthélemy et. al. to be r(D) = |V (T )| − |V (D)|. We will completely determine the reversing number for a disjoint union of directed stars and begin to investigate the problem for the general class of arborescences. AMS Classification: Primary: 05C20, Secondary: 90C47
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