The effect of updates in binary search trees

  • Authors:
  • J C Culberson

  • Affiliations:
  • Data Structuring Group, Department of Computer Science, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada

  • Venue:
  • STOC '85 Proceedings of the seventeenth annual ACM symposium on Theory of computing
  • Year:
  • 1985

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Abstract

If a binary search tree is created by inserting N keys in random order using the usual insertion algorithm, then it is well known that the average search path is about 1.4lgN. However, if deletions, using the frequently recommended Hibbard's algorithm, are interspersed with the insertions, then virtually nothing has been proven except for Knuth and Jonassen's very difficult, but complete, analysis of the case N = 3. In this paper it is shown that after a sufficient number of updates the average search path is &thgr;(N1/2). An improved algorithm given by Knuth is shown to have the same asymptotic behavior.