Approximating a minimum Manhattan network

  • Authors:
  • Joachim Gudmundsson;Christos Levcopoulos;Giri Narasimhan

  • Affiliations:
  • -;-;-

  • Venue:
  • Nordic Journal of Computing
  • Year:
  • 2001

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Abstract

Given a set S of n points in the plane, we define a Manhattan Network on S as a rectilinear network G with the property that for every pair of points in S, the network G contains the shortest rectilinear path between them. A Minimum Manhattan Network on S is a Manhattan network of minimum possible length. A Manhattan network can be thought of as a graph G=(V,E), where the vertex set V corresponds to points from S and a set of Steiner points S', and the edges in E correspond to horizontal or vertical line segments connecting points in S U S'. A Manhattan network can also be thought of as a 1-spanner (for the L1-metric) for the points in S.Let R be an algorithm that produces a rectangulation of a staircase polygon in time R(n) of weight at most r times the optimal. We design an O(n\log n + R(n)) time algorithm which, given a set S of n points in the plane, produces a Manhattan network on S with total weight at most 4r times that of a minimum Manhattan network. Using known rectangulation algorithms, this gives us an O(n3)-time algorithm with approximation factor four, and an O(n \log n)-time algorithm with approximation factor eight.