On using conditional rotation operations to adaptively structure binary search trees

  • R. P. Cheetham
  • B. J. Oommen
  • D. T. H. Ng
Complexity And Optimization
Part of the Lecture Notes in Computer Science book series (LNCS, volume 326)


Consider a set
of records, where each record is identified by a unique key. The records are accessed based on a set of access probabilities
and are to be arranged lexicographically using a binary search tree. If
is known a priori, it is well known [7] that an optimal binary search tree may be constructed using
. We consider the case when
is not known a priori. A new restructuring heuristic is introduced that requires three extra integer memory locations per record, and this restructuring of the tree is performed only if it decreases the weighted path length of the overall resultant tree. We also present a space optimized version of the latter restructuring mechanism which requires only one extra integer field per record. We show that the cost of the tree is reduced by each restructuring operation, and present experimental results to demonstrate the superiority of our algorithm over all other reported efficient static and dynamic schemes.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1988

Authors and Affiliations

  • R. P. Cheetham
    • 1
  • B. J. Oommen
    • 1
  • D. T. H. Ng
    • 1
  1. 1.School of Computer ScienceCarleton UniversityOttawaCanada

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