An approximation for finding a smallest 2-edge-connected subgraph containing a specified spanning tree

  • Authors:
  • Hiroshi Nagamochi

  • Affiliations:
  • Department of Information and Computer Sciences, Toyohashi University of Technology, Hibarigaoka Tempaku, Toyohashi Aichi, 4 1-8580, Japan

  • Venue:
  • Discrete Applied Mathematics - Special issue: Special issue devoted to the fifth annual international computing and combinatories conference (COCOON'99) Tokyo, Japan 26-28 July 1999
  • Year:
  • 2003

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Abstract

Given a graph G=(V,E) and a tree T =(V,F) with E ∩ F = φ such that G + T =(V,F ∪ E) is 2-edge-connected, we consider the problem of finding a smallest 2-edge-connected spanning subgraph (V,F ∪ E') of G + T containing T. The problem, which is known to be NP-hard, admits a 2-approximation algorithm. However, obtaining a factor better than 2 for this problem has been one of the main open problems in the graph augmentation problem. In this paper, we show that the problem is (1.875 + ε)-approximable in O(n½m + n2) time for any constant ε n = |V| and m = |E ∪ F|.