Corner cuts are close to optimal: From solid grids to polygons and back

  • Authors:
  • Andreas Emil Feldmann;Shantanu Das;Peter Widmayer

  • Affiliations:
  • University of Waterloo, Combinatorics and Optimization Department, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada;Technion-Israel Institute of Technology, Faculty of Industrial Engineering and Management, Technion City, Haifa 32000, Israel;ETH Zurich, Institut für Theoretische Informatik, CAB H 39.2, Universitätstrasse 6, 8092 Zürich, Switzerland

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2013

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Abstract

We study the solution quality for min-cut problems on graphs when restricting the shapes of the allowed cuts. In particular we are interested in min-cut problems with additional size constraints on the parts being cut out from the graph. Such problems include the bisection problem, the separator problem, or the sparsest cut problem. We therefore aim at cutting out a given number m of vertices from a graph using as few edges as possible. We consider this problem on solid grid graphs, which are finite, connected subgraphs of the infinite two-dimensional grid that do not have holes. Our interest is in the tradeoff between the simplicity of the cut shapes and their solution quality: we study corner cuts in which each cut has at most one right-angled bend. We prove that optimum corner cuts get us arbitrarily close to a cut-out part of size m, and that this limitation makes us lose only a constant factor in the quality of the solution. We obtain our result by a thorough study of cuts in polygons and the effect of limiting these to corner cuts.