A (slightly) faster algorithm for Klee's measure problem

  • Authors:
  • Timothy M. Chan

  • Affiliations:
  • School of Computer Science, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada

  • Venue:
  • Computational Geometry: Theory and Applications
  • Year:
  • 2010

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Abstract

Given n axis-parallel boxes in a fixed dimension d=3, how efficiently can we compute the volume of the union? This standard problem in computational geometry, commonly referred to as Klee's measure problem, can be solved in time O(n^d^/^2logn) by an algorithm of Overmars and Yap (FOCS 1988). We give the first (albeit small) improvement: our new algorithm runs in time n^d^/^22^O^(^l^o^g^^^*^n^), where log^* denotes the iterated logarithm. For the related problem of computing the depth in an arrangement of n boxes, we further improve the time bound to near O(n^d^/^2/log^d^/^2^-^1n), ignoring loglogn factors. Other applications and lower-bound possibilities are discussed. The ideas behind the improved algorithms are simple.