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, 2004 route des Lucioles, BP 93 F-06902, Sophia Antipolis Cedex, France;Department of Informatics, University of Bergen, POB 7803, 5020 Bergen, Norway;Department of Computer Science, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK;Department of Computer Science, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK;Department of Informatics, University of Bergen, POB 7803, 5020 Bergen, Norway;Department of Computer Science, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK

  • Venue:
  • Journal of Computer and System Sciences
  • Year:
  • 2010

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Abstract

An out-tree T is an oriented tree with only one vertex of in-degree zero. A vertex x of T is internal if its out-degree is positive. We design randomized and deterministic algorithms for deciding whether an input digraph contains a given out-tree with k vertices. The algorithms are of running time O^*(5.704^k) and O^*(6.14^k), respectively. We apply the deterministic algorithm to obtain a deterministic 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) [9].