On Levels in Arrangements of Curves, II: A Simple Inequality and Its Consequences

  • Authors:
  • Timothy M. Chan

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

  • Venue:
  • Discrete & Computational Geometry
  • Year:
  • 2005

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Abstract

We give a surprisingly short proof that in any planar arrangement of n curves where each pair intersects at most a fixed number (s) of times, the k-level has subquadratic (O(n2-1/2s) complexity. This answers one of the main open problems from the author’s previous paper [DCG 29, 375-393 (2003)], which provided a weaker upper bound for a restricted class of curves only (graphs of degree-s polynomials). When combined with existing tools (cutting curves, sampling, etc.), the new idea generates a slew of improved k-level results for most of the curve families studied earlier, including a near-O(n3/2 bound for parabolas.