Algorithm for Finding k-Vertex Out-trees and Its Application to k-Internal Out-branching Problem

  • Authors:
  • Nathann Cohen;Fedor V. Fomin;Gregory Gutin;Eun Jung Kim;Saket Saurabh;Anders Yeo

  • Affiliations:
  • INRIA --- Projet MASCOTTE, Sophia Antipolis Cedex, France F-06902;Department of Informatics, University of Bergen, Bergen, Norway POB 7803, 5020;Department of Computer Science Royal Holloway, University of London, UK TW20 0EX;Department of Computer Science Royal Holloway, University of London, UK TW20 0EX;Department of Informatics, University of Bergen, Bergen, Norway POB 7803, 5020;Department of Computer Science Royal Holloway, University of London, UK TW20 0EX

  • Venue:
  • COCOON '09 Proceedings of the 15th Annual International Conference on Computing and Combinatorics
  • Year:
  • 2009

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Abstract

An out-tree T is an oriented tree with exactly one vertex of in-degree zero and a vertex x of T is called internal if its out-degree is positive. We design randomized and deterministic algorithms for deciding whether an input digraph contains a subgraph isomorphic to a given out-tree with k vertices. Both algorithms run in O *(5.704 k ) time. We apply the deterministic algorithm to obtain an algorithm of runtime O *(c k ), where c is a constant, for deciding whether an input digraph contains a spanning out-tree with at least k internal vertices. This answers in affirmative a question of Gutin, Razgon and Kim (Proc. AAIM'08).