Improved bounds for range mode and range median queries

  • Authors:
  • Holger Petersen

  • Affiliations:
  • Univ. Stuttgart, FMI, Stuttgart

  • Venue:
  • SOFSEM'08 Proceedings of the 34th conference on Current trends in theory and practice of computer science
  • Year:
  • 2008

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Abstract

We investigate the following problem: Given a list of n items and a function defined over lists of these items, generate a bounded amount of auxiliary information such that range queries asking for the value of the function on sub-lists can be answered within a certain time bound. For the function "mode" we improve the previously known time bound O(nƐ log n) to O(nƐ) with space O(n2-2Ɛ), where 0 ≤ Ɛ O(n2 log log n/ log n) for an O(1) time bounded solution to O(n2/ log n). For the function "median" the space bound O(n2 log log n/ log n) is improved to O(n2 log(k) n/ log n) for an O(1) time solution, where k is an arbitrary constant and log(k) is the iterated logarithm.