Rectilinear Shortest Paths and Minimum Spanning Trees in the Presence of Rectilinear Obstacles

  • Authors:
  • Ying-Fung Wu;Peter Widmayer;Martine D. F. Schlag;C. K. Wong

  • Affiliations:
  • Microelectronics and Computer Technology Corporation, Austin, TX;Univ. of Karlsruhe, Karlsruhe, W. Germany;Univ. of California, Los Angeles;IBM T. J. Watson Research Center, Yorktown Heights, NY

  • Venue:
  • IEEE Transactions on Computers
  • Year:
  • 1987

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Abstract

We study the rectilinear shortest paths and minimum spanning tree (MST) problems for a set of points in the plane in the presence of rectilinear obstacles. We use the track graph, a suitably defined grid-like structure, to obtain efficient solutions for both problems. The track graph consists of rectilinear tracks defined by the obstacles and the points for which shortest paths and a minimum spanning tree are sought. We use a growth process like Dijkstra's on the track graph to find shortest paths from any point in the set to all other points (the one-to-all shortest paths problem). For the one-to-all shortest paths problem for n points we derive an O(n min {log n, log e} + (e + k) log t) time algorithm, where e is the total number of edges of all obstacles, t is the number of extreme edges of all obstacles, and k is the number of intersections among obstacle tracks (all bounds are for the worst case). The MST for the points is constructed also in time O(n log n + (e + k) log t) by a hybrid method of searching for shortest paths while simultaneously constructing an MST. An interesting application of the MST algorithm is the approximation of Steiner trees in graphs.