Point Location in o(log n) Time, Voronoi Diagrams in o(n log n) Time, and Other Transdichotomous Results in Computational Geometry

  • Authors:
  • Timothy M. Chan

  • Affiliations:
  • University of Waterloo, Canada

  • Venue:
  • FOCS '06 Proceedings of the 47th Annual IEEE Symposium on Foundations of Computer Science
  • Year:
  • 2006

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Abstract

Given n points in the plane with integer coordinates bounded by U \leqslant2^{w}, we show that the Voronoi diagram can be constructed in O(min{n logn/loglogn, n\sqrt {\log U}) expected time by a randomized algorithm on the unit-cost RAM with word size w. Similar results are also obtained for many other fundamental problems in computational geometry, such as constructing the convex hull of a 3-dimensional point set, computing the Euclidean minimum spanning tree of a planar point set, triangulating a polygon with holes, and finding intersections among a set of line segments. These are the first results to beat the \Omega(nlogn) algebraic-decision-tree lower bounds known for these problems. The results are all derived from a new twodimensional version of fusion trees that can answer point location queries in O(min{logn/loglogn, \sqrt {\log U})time with linear space. Higher-dimensional extensions and applications are also mentioned in the paper.