On the Number of Acyclic Orientations of Complete $k$-Partite Graphs

Abstract

Building on previous work by Cameron et al. in [3], we give a recurrence for computing the number of acyclic orientations of complete k-partite graphs, which can be implemented to obtain a dynamic programming algorithm running in time n O(k) , where n is the number of vertices in the graph. We prove our result by using a relationship between the number of acyclic orientations and the number of Hamiltonian paths in complete k-partite graphs and providing a recurrence for the latter quantity. We give a simple extension of our algorithm to the situation when we are an edge removal away from having a complete k-partite graph.