Searching a Circular Corridor with Two Flashlights

  • Authors:
  • Bo Jiang;Xuehou Tan

  • Affiliations:
  • School of Inform. Sci. and Tech., Dalian Martime University, China;School of Inform. Sci. and Tech., Dalian Martime University, China and Tokai University, Numazu, Japan 410-0395

  • Venue:
  • TAMC '09 Proceedings of the 6th Annual Conference on Theory and Applications of Models of Computation
  • Year:
  • 2009

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Abstract

We consider the problem of searching for a mobile intruder in a circular corridor (a polygon with one polygonal hole) by two searchers, who hold a flashlight. Both searchers move on the outer boundary, directing their flashlights at the inner boundary. The objective is to decide whether there exists a search schedule for the searchers to detect the intruder, no matter how fast he moves. We give a characterization of the class of circular corridors, which are searchable with two flashlights. Based on our characterization, an O (n logn ) time algorithm is then presented to determine the searchability of a circular corridor with two flashlights, where n denotes the total number of vertices of the outer and inner boundaries. Moreover, a search schedule can be output in time linear in its size, if it exists. Our result gives the first efficient solution to the polygon search problem for two searchers.