EULERIAN AND HAMILTONIAN DICYCLES IN DIRECTED HYPERGRAPHS

Abstract

In this paper, we generalize the concepts of Eulerian and Hamiltonian digraphs to directed hypergraphs. A dihypergraphH is a pair (𝒱(H), ℰ(H)), where 𝒱(H) is a non-empty set of elements, called vertices, and ℰ(H) is a collection of ordered pairs of subsets of 𝒱(H), called hyperarcs. It is Eulerian (resp. Hamiltonian) if there is a dicycle containing each hyperarc (resp. each vertex) exactly once. We first present some properties of Eulerian and Hamiltonian dihypergraphs. For example, we show that deciding whether a dihypergraph is Eulerian is an NP-complete problem. We also study when iterated line dihypergraphs are Eulerian and Hamiltonian. Finally, we study when the generalized de Bruijn dihypergraphs are Eulerian and Hamiltonian. In particular, we determine when they contain a complete Berge dicycle, i.e., an Eulerian and Hamiltonian dicycle.