Digital Search Trees Again Revisited: The Internal Path Length Perspective

  • Authors:
  • Peter Kirschenhofer;Helmut Prodinger;Wojciech Szpankowski

  • Affiliations:
  • -;-;-

  • Venue:
  • SIAM Journal on Computing
  • Year:
  • 1994

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Abstract

This paper studies the asymptotics of the variance for the internal path length in a symmetric digital search tree under the Bernoulli model. This problem has been open until now. It is proved that the variance is asymptotically equal to $N\cdot0.26600 +N\cdot\delta(\log_2 N),$ where $N$ is the number of stored records and $\delta(x)$ is a periodic function of mean zero and a very small amplitude. This result completes a series of studies devoted to the asymptotic analysis of the variances of digital tree parameters in the symmetric case. In order to prove the previous result a number of nontrivial problems concerning analytic continuations and some others of a numerical nature had to be solved. In fact, some of these techniques are motivated by the methodology introduced in an influential paper by Flajolet and Sedgewick.