Partially complemented representations of digraphs

Elias Dahlhaus, Jens Gustedt, Ross M. Mcconnell
2002 Discrete Mathematics & Theoretical Computer Science  
Special issue: Graph Decompositions International audience A complementation operation on a vertex of a digraph changes all outgoing arcs into non-arcs, and outgoing non-arcs into arcs. This defines an equivalence relation where two digraphs are equivalent if one can be obtained from the other by a sequence of such operations. We show that given an adjacency-list representation of a digraph G, many fundamental graph algorithms can be carried out on any member G' of G's equivalence class in
more » ... ) time, where m is the number of arcs in G, not the number of arcs in G' . This may have advantages when G' is much larger than G. We use this to generalize to digraphs a simple O(n + m log n) algorithm of McConnell and Spinrad for finding the modular decomposition of undirected graphs. A key step is finding the strongly-connected components of a digraph F in G's equivalence class, where F may have ~(m log n) arcs.
doi:10.46298/dmtcs.303 fatcat:j4ff7pdsbrhythdzvcdahreiyu