Partial match queries in random quadtrees

  • Authors:
  • Nicolas Broutin;Ralph Neininger;Henning Sulzbach

  • Affiliations:
  • INRIA Rocquencourt, Le Chesnay, France;J.W. Goethe University, Frankfurt am Main, Germany;J.W. Goethe University, Frankfurt am Main, Germany

  • Venue:
  • Proceedings of the twenty-third annual ACM-SIAM symposium on Discrete Algorithms
  • Year:
  • 2012

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Abstract

We consider the problem of recovering items matching a partially specified pattern in multidimensional trees (quad trees and k-d trees). We assume the traditional model where the data consist of independent and uniform points in the unit square. For this model, in a structure on n points, it is known that the number of nodes Cn (ζ) to visit in order to report the items matching an independent and uniformly on [0, 1] random query ζ satisfies E[Cn(ζ)] ~ κnβ, where κ and β are explicit constants. We develop an approach based on the analysis of the cost Cn(x) of any fixed query x ε [0, 1], and give precise estimates for the variance and limit distribution of the cost Cn(x). Our results permit to describe a limit process for the costs Cn(x) as x varies in [0, 1]; one of the consequences is that E[maxxε[0, 1] Cn(x)] ~ γnβ; this settles a question of Devroye [Pers. Comm., 2000].