Discrete & Computational Geometry

, Volume 5, Issue 5, pp 427–448

Construction of ɛ-nets

  • Jiří Matoušek

DOI: 10.1007/BF02187804

Cite this article as:
Matoušek, J. Discrete Comput Geom (1990) 5: 427. doi:10.1007/BF02187804


LetS be a set ofn points in the plane and letɛ be a real number, 0<ɛ<1. We give a deterministic algorithm, which in timeO(−2 log(1/ɛ)+ɛ−8) (resp.O(−2 log(1/ɛ)+ɛ−10) constructs anɛ-netNS of sizeO((1/ɛ) (log(1/ɛ))2) for intersections ofS with double wedges (resp. triangles); this means that any double wedge (resp. triangle) containing more thatɛn points ofS contains a point ofN. This givesO(n logn) deterministic preprocessing for the simplex range-counting algorithm of Haussler and Welzl [HW] (in the plane).

We also prove that given a setL ofn lines in the plane, we can cut the plane intoO(ɛ−2) triangles in such a way that no triangle is intersected by more thanɛn lines ofL. We give a deterministic algorithm for this with running timeO(−2 log(1/ɛ)). This has numerous applications in various computational geometry problems.

Copyright information

© Springer-Verlag New York Inc. 1990

Authors and Affiliations

  • Jiří Matoušek
    • 1
  1. 1.Department of Computer ScienceCharles UniversityPraha 1Czechoslovakia