2026-08-08T08:28:17Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:13305 2024-03-06T10:51:39Z ddc:004 open_access

Component Order Connectivity in Directed Graphs Bang-Jensen, Jørgen Eiben, Eduard Gutin, Gregory Wahlström, Magnus Yeo, Anders Parameterized Algorithms component order connectivity directed graphs semicomplete digraphs A directed graph D is semicomplete if for every pair x,y of vertices of D, there is at least one arc between x and y. Thus, a tournament is a semicomplete digraph. In the Directed Component Order Connectivity (DCOC) problem, given a digraph D = (V,A) and a pair of natural numbers k and 𝓁, we are to decide whether there is a subset X of V of size k such that the largest strong connectivity component in D-X has at most 𝓁 vertices. Note that DCOC reduces to the Directed Feedback Vertex Set problem for 𝓁 = 1. We study parameterized complexity of DCOC for general and semicomplete digraphs with the following parameters: k, 𝓁, 𝓁+k and n-𝓁. In particular, we prove that DCOC with parameter k on semicomplete digraphs can be solved in time O^*(2^(16k)) but not in time O^*(2^o(k)) unless the Exponential Time Hypothesis (ETH) fails. The upper bound O^*(2^(16k)) implies the upper bound O^*(2^(16(n-𝓁))) for the parameter n-𝓁. We complement the latter by showing that there is no algorithm of time complexity O^*(2^o(n-𝓁)) unless ETH fails. Finally, we improve (in dependency on 𝓁) the upper bound of Göke, Marx and Mnich (2019) for the time complexity of DCOC with parameter 𝓁+k on general digraphs from O^*(2^O(k𝓁 log (k𝓁))) to O^*(2^O(klog (k𝓁))). Note that Drange, Dregi and van 't Hof (2016) proved that even for the undirected version of DCOC on split graphs there is no algorithm of running time O^*(2^o(klog 𝓁)) unless ETH fails and it is a long-standing problem to decide whether Directed Feedback Vertex Set admits an algorithm of time complexity O^*(2^o(klog k)). Schloss Dagstuhl – Leibniz-Zentrum für Informatik Jørgen Bang-Jensen and Eduard Eiben and Gregory Gutin and Magnus Wahlström and Anders Yeo 2020 Is Part Of LIPIcs, Volume 180, 15th International Symposium on Parameterized and Exact Computation (IPEC 2020) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.IPEC.2020.2 urn:nbn:de:0030-drops-133058 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2020.2 eng https://creativecommons.org/licenses/by/3.0/legalcode