Computing homotopic shortest paths in the plane

  • Authors:
  • Sergei Bespamyatnikh

  • Affiliations:
  • Department of Computer Science, University of Texas at Dallas, Box 830688, Richardson, TX

  • Venue:
  • Journal of Algorithms
  • Year:
  • 2003

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Abstract

We address the problem of computing homotopic shortest paths in the presence of obstacles in the plane. Problems on homotopy of paths received attention very recently [Cabello et al., in: Proc. 18th Annu. ACM Sympos. Comput. Geom., 2002, pp. 160-169; Efrat et al., in: Proc. 10th Annu. European Sympos. Algorithms, 2002, pp. 411-423]. We present two output-sensitive algorithms, for simple paths and non-simple paths. The algorithm for simple paths improves the previous algorithm [Efrat et al., in: Proc. 10th Annu. European Sympos. Algorithms, 2002, pp. 411-423]. The algorithm for non-simple paths achieves O(log2n) time per output vertex which is an improvement by a factor of O(n/log2n) of the previous algorithm [Hershberger, Snoeyink, Comput. Geom. Theory Appl. 4 (1994) 63-98], where n is the number of obstacles. The running time has an overhead O(n2+ε) for any positive constant ε. In the case k 2+ε, where k is the total size of the input and output, we improve the running to O((n + k + (nk)2/3) logO(1) n).