PTAS for geometric hitting set problems via local search

  • Authors:
  • Nabil Hassan Mustafa;Saurabh Ray

  • Affiliations:
  • Lahore University of Management Sciences, Lahore, Pakistan;Universitaet des Saarlandes, Saarbruecken, Germany

  • Venue:
  • Proceedings of the twenty-fifth annual symposium on Computational geometry
  • Year:
  • 2009

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Abstract

We consider the problem of computing minimum geometric hitting sets in which, given a set of geometric objects and a set of points, the goal is to compute the smallest subset of points that hit all geometric objects. The problem is known to be strongly NP-hard even for simple geometric objects like unit disks in the plane. Therefore, unless P=NP, it is not possible to get Fully Polynomial Time Approximation Algorithms (FPTAS) for such problems. We give the first PTAS for this problem when the geometric objects are half-spaces in Re3 and when they are an r-admissible set regions in the plane (this includes pseudo-disks as they are 2-admissible). Quite surprisingly, our algorithm is a very simple local search algorithm which iterates over local improvements only.