Long non-crossing configurations in the plane

  • Authors:
  • Noga Alon;Sridhar Rajagopalan;Subhash Suri

  • Affiliations:
  • -;-;-

  • Venue:
  • SCG '93 Proceedings of the ninth annual symposium on Computational geometry
  • Year:
  • 1993

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Abstract

We study some geometric maximization problems in theEuclidean plane under the non-crossing constraint. Given a setV of2n points in general position in theplane, we investigate the following geometric configurations usingstraight-line segments and the Euclidean norm: (i) longest non-crossingmatching, (ii) longest non-crossing hamiltonian path, (iii) longestnon-crossing spanning tree. We propose simple and efficient algorithmsto approximate these structures within a constant factor of optimality.Somewhat surprisingly, we also show that our bounds are within aconstant factor of optimality even without the non-crossing constraint.For instance, we give an algorithm to compute a non-crossing matchingwhose total length is at least 2/&pgr; of the longest (possiblycrossing) matching, and show that the ratio 2/&pgr; between thenon-crossing and crossing matching is the best possible. Perhaps due totheir utter simplicity, our methods also seem more general and amenableto applications in other similar contexts.