Probabilistic behavior of asymmetric level compressed tries

  • Authors:
  • Luc Devroye;Wojcieh Szpankowski

  • Affiliations:
  • School of Computer Science, McGill University, 3480 University Street, Montreal H3A 2K6, Canada;Department of Computer Sciences, Purdue University, 250 North University Street, West Lafayette, Indiana, 47907-2066

  • Venue:
  • Random Structures & Algorithms
  • Year:
  • 2005

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Abstract

Level-Compressed (in short LC) tries were introduced by Andersson and Nilsson in 1993. They are compacted versions of tries in which, from the top down, maximal height complete subtrees are level compressed. We show that when the input consists of n independent strings with independent Bernoulli (p) bits, p ≠ 1/2, then the expected depth of a typical node is in probability asymptotic to $${{\rm log\,\,log}\,\,n} \over {\rm log}\,\, \left(1 - {{\cal H} \over {\cal H} - \infty}\right)$$ where H - p log p - (1 - p) log (1 - p) is the Shannon entropy of the source, and H-∞ = log (1 / min(p, 1 - p)). The height is in probability asymptotic to $${{\rm log}\,\,n}\,\, \over {\cal H}_2$$ where H2 = log(1/(p2 + (1-p)2)). © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2005