Computing the all-pairs longest chains in the plane

  • Mikhail J. Atallah
  • Danny Z. Chen
Invited Presentations
Part of the Lecture Notes in Computer Science book series (LNCS, volume 709)

Abstract

Many problems on sequences and on circular-arc graphs involve the computation of longest chains between points in the plane. Given a set S of n points in the plane, we consider the problem of computing the matrix of longest chain lengths between all pairs of points in S, and the matrix of “parent” pointers that describes the n longest chain trees. We present a simple sequential algorithm for computing these matrices. Our algorithm runs in O(n2) time, and hence is optimal. We also present a rather involved parallel algorithm that computes these matrices in O(log2n) time using O(n2/log n) processors in the CREW PRAM model. These matrices enables us to report, in O(1) time, the length of a longest chain between any two points in S by using one processor, and the actual chain by using k processors, where k is the number of points of S on that chain. The space complexity of the algorithms is O(n2).

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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Mikhail J. Atallah
    • 1
  • Danny Z. Chen
    • 2
  1. 1.Dept. of Computer SciencePurdue UniversityWest Lafayette
  2. 2.Department of Computer Science and EngineeringUniversity of Notre DameNotre Dame

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