Clustering Cycles into Cycles of Clusters

In this paper we study simple families of clustered graphs that are highly unconnected. We start by studying 3-cluster cycles, which are clustered graphs such that the underlying graph is a simple cycle and there are three clusters all at the same level. We show that in this case, testing the c-planarity can be done efficiently and give an efficient drawing algorithm. Also, we characterize 3-cluster cycles in terms of formal grammars. Finally, we generalize the results on 3-cluster cycles considering clustered graphs that have a cycle structure at each level of the inclusion tree. We present efficient c-planarity testing and drawing algorithms also for this case. -