Geometric separation and exact solutions for the parameterized independent set problem on disk graphs

  • Authors:
  • Jochen Alber;Jiří Fiala

  • Affiliations:
  • Wilhelm-Schickard-Institut für Informatik, Universität Tübingen, Sand 13, D-72076 Tübingen, Germany;Charles University, Faculty of Mathematics and Physics, Department of Aplied Mathematics, DIMATIA and Institute for Theoretical Computer Science (ITI), 3 Malostranské nám. 2/25, 11800 Pr ...

  • Venue:
  • Journal of Algorithms
  • Year:
  • 2004

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Abstract

We consider the parameterized probleln, whether for a given set D of n disks (of bounded radius ratio) in the Euclidean plane there exists a set of k non-intersecting disks. For this problem, we expose an algorithm running in time nO(√k) that is--to our knowledge--the first algorithm with running time bounded by an exponential with a sublinear exponent. For γ-precision disk graphs of bounded radius ratio, we show that the problem is fixed parameter tractable with a running time 2O(√k) + nO(1). The results are based on problem kernelization and a new "geometric (√ċ--separator) theorem" which holds for all disk graphs of bounded radius ratio. The presented algorithm then performs, in a first step, a "geometric problem kernelization" and, in a second step, uses divide-and-conquer based on our new "geometric separator theorem."