In recent years, the combinatorics of argumentation with arguments that can attack each other has been studied extensively. Especially, attack graphs (put in the focus of attention by Dung's seminal work 1995) have proven to be a productive tool of analysis. In this paper a new style of algorithm is presented that computes the minimal admissible sets containing or attacking the argument. It is a breadth-first algorithm using labelings. The algorithm is applied to the computation of the preferred and stable extensions of a given attack graph.