The 2-center problem with obstacles

  • Authors:
  • Dan Halperin;Micha Sharir;Ken Goldberg

  • Affiliations:
  • School of Computer Science, Tel Aviv University, Tel-Aviv 69978, Israel;School of Computer Science, Tel Aviv University, Tel-Aviv 69978, Israel/ and Courant Institute of Mathematical Sciences, New York University, New York;Department of Industrial Engineering and Operations Research, University of California, Berkeley, California

  • Venue:
  • Journal of Algorithms
  • Year:
  • 2002

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Abstract

Given a set S of n points in the plane and a set O of pairwise disjoint simple polygons with a total of m edges, we wish to find two congruent disks of smallest radius whose union covers S and whose centers lie outside the polygons in O (referred to as locational constraints in facility location theory). We present an algorithm to solve this problem in randomized expected time O(m log2(mn) + mn log2 n log(mn)). We also present an efficient approximation scheme that constructs, for a given ε 0, two disks as above of radius at most (1 + ε)r*, where r* is the optimal radius, in time O(1/ε log(1/ε)(m log2 m + n log2 n)) or in randomized expected time O(1/ε log(1/ε)((m + n log n) log(mn))).