On Enumerating Minimal Dicuts and Strongly Connected Subgraphs

  • Authors:
  • Leonid Khachiyan;Endre Boros;Khaled Elbassioni;Vladimir Gurvich

  • Affiliations:
  • -;Rutgers University, RUTCOR, 640 Bartholomew Road, 08854-8003, Piscataway, NJ, USA;Max-Planck-Institut für Informatik, 640 Bartholomew Road, 08854-8003, Saarbrücken, NJ, Germany;Rutgers University, RUTCOR, 640 Bartholomew Road, 08854-8003, Piscataway, NJ, USA

  • Venue:
  • Algorithmica
  • Year:
  • 2007

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Abstract

We consider the problems of enumerating all minimal strongly connected subgraphs and all minimal dicuts of a given strongly connected directed graph G=(V,E). We show that the first of these problems can be solved in incremental polynomial time, while the second problem is NP-hard: given a collection of minimal dicuts for G, it is NP-hard to tell whether it can be extended. The latter result implies, in particular, that for a given set of points $\mathcal{A}\subseteq\mathbb{R}^{n}$, it is NP-hard to generate all maximal subsets of $\mathcal{A}$ contained in a closed half-space through the origin. We also discuss the enumeration of all minimal subsets of $\mathcal{A}$ whose convex hull contains the origin as an interior point, and show that this problem includes as a special case the well-known hypergraph transversal problem.