Approximating Steiner k-cuts

  • Authors:
  • Chandra Chekuri;Sudipto Guha;Joseph Naor

  • Affiliations:
  • Bell Labs, Murray Hill, NJ;Dept. of Computer & Information Science, University of Pennsylvania, Philadelphia, PA;Computer Science Dept., Technion, Haifa, Israel

  • Venue:
  • ICALP'03 Proceedings of the 30th international conference on Automata, languages and programming
  • Year:
  • 2003

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Abstract

We consider the Steiner k-cut problem, which is a common generalization of the k-cut problem and the multiway cut problem: given an edge-weighted undirected graph G = (V,E), a subset ofv ertices X ⊆ V called terminals, and an integer k ≤ |X|, the objective is to find a minimum weight set of edges whose removal results in k disconnected components, each ofwhic h contains at least one terminal. We give two approximation algorithms for the problem: a 2 - 2/k-approximation based on Gomory-Hu trees, and a 2 - 2/|X|-approximation based on LP rounding. The latter algorithm is based on rounding a generalization of a linear programming relaxation suggested by Naor and Rabani [8]. The rounding uses the Goemans and Williamson primal-dual algorithm (and analysis) for the Steiner tree problem [4] in an interesting way and differs from the rounding in [8]. We use the insight from the rounding to develop an exact bi-directed formulation for the global minimum cut problem (the k-cut problem with k = 2).