On computing minimum (s,t)-cuts in digraphs

  • Authors:
  • Hiroshi Nagamochi

  • Affiliations:
  • Department of Applied Mathematics and Physics, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan

  • Venue:
  • Information Processing Letters
  • Year:
  • 2005

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Abstract

Let D=(V,E) be a simple digraph with n vertices and m edges, and s and t be vertices designated as a source and a sink. The currently fastest algorithm that computes a minimum (s,t)-cut in D runs in O(min{@n,n^2^/^3,m^1^/^2}m) time, where @n is the size of a minimum (s,t)-cut. In this paper, we define the non-eulerianness @m as the sum of |#incoming edges at u-#outgoing edges at u| over all u@?V-{s,t}, and prove that a minimum (s,t)-cut in D can be obtained in O(min{m+@n(@n+@m)^1^/^2n,(@n+@m)^1^/^6nm^2^/^3}) time. This outperforms the previous algorithm when D is a dense digraph with small @m.