Guarding Art Galleries: The Extra Cost for Sculptures Is Linear

  • Authors:
  • Louigi Addario-Berry;Omid Amini;Jean-Sébastien Sereni;Stéphan Thomassé

  • Affiliations:
  • Department of Statistics, Oxford University, Oxford, UK;Max-Planck-Institut für Informatik, Saarbrücken, Germany;Institute for Theoretical Computer Science and Department of Applied Mathematics, Charles University, Prague, Czech Republic;LIRMM-Université Montpellier II, Montpellier, France

  • Venue:
  • SWAT '08 Proceedings of the 11th Scandinavian workshop on Algorithm Theory
  • Year:
  • 2008

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Abstract

Art gallery problems have been extensively studied over the last decade and have found different type of applications. Normally the number of sides of a polygon or the general shape of the polygon is used as a measure of the complexity of the problem. In this paper we explore another measure of complexity, namely, the number of guards required to guard the boundary, or the walls, of the gallery. We prove that if nguards are necessary to guard the walls of an art gallery, then an additional team of at most 4n茂戮驴 6 will guard the whole gallery. This result improves a previously known quadratic bound, and is a step towards a possibly optimal value of n茂戮驴 2 additional guards. The proof is algorithmic, uses ideas from graph theory, and is mainly based on the definition of a new reduction operator which recursively eliminates the simple parts of the polygon. We also prove that every gallery with cconvex vertices can be guarded by at most 2c茂戮驴 4 guards, which is optimal.