Largest empty circle centered on a query line

  • Authors:
  • John Augustine;Brian Putnam;Sasanka Roy

  • Affiliations:
  • School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371;HMC, 300 Chestnut St, Suite 101, Needham, MA 02492, USA;CSA Department, Indian Institute of Science, Bangalore 560012, India

  • Venue:
  • Journal of Discrete Algorithms
  • Year:
  • 2010

Quantified Score

Hi-index 0.00

Visualization

Abstract

The Largest Empty Circle problem seeks the largest circle centered within the convex hull of a set P of n points in R^2 and devoid of points from P. In this paper, we introduce a query version of this well-studied problem. In our query version, we are required to preprocess P so that when given a query line Q, we can quickly compute the largest empty circle centered at some point on Q and within the convex hull of P. We present solutions for two special cases and the general case; all our queries run in O(logn) time. We restrict the query line to be horizontal in the first special case, which we preprocess in O(n@a(n)logn) time and space, where @a(n) is the slow growing inverse of Ackermann's function. When the query line is restricted to pass through a fixed point, the second special case, our preprocessing takes O(n@a(n)^O^(^@a^(^n^)^)logn) time and space. We use insights from the two special cases to solve the general version of the problem with preprocessing time and space in O(n^3logn) and O(n^3) respectively.