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An (n; s) Davenport{Schinzel sequence, for positive integers n and s, is a sequence composed of n distinct symbols with the properties that no two adjacent elements are equal, and that it does not contain, as a (possibly non-contiguous) subsequence, any alternation a b a b of length s + 2 between two distinct symbols a and b. The close relationship between(More)
We present a simple randomized algorithm which solves linear programs with <italic>n</italic> constraints and <italic>d</italic> variables in expected <italic>O</italic>(<italic>nde</italic><supscrpt>(<italic>d</italic> ln(<italic>n</italic>+1))<supscrpt>1/4</supscrpt></supscrpt>) time in the unit cost model (where we count the number of arithmetic(More)
Davenport-Schinzel sequences are sequences that do not contain forbidden subsequences of alternating symbols. They arise in the computation of the envelope of a set of functions. We show that the maximal length of a Davenport-Schinzel sequence composed of n symbols is 6(noc(n»), where t1.(n)is the functional inverse of Ackermann's function, and is thus very(More)
We study the criteria under which an object can be gripped by a multifingered dexterous hand, assuming no static friction between the object and the fingers; such grips are calledpositive grips. We study three cases in detail: (i) the body is at equilibrium, (ii) the body is under some constant external force/torque, and (iii) the body is under a varying(More)
Given a triangulation of a simple polygonP, we present linear-time algorithms for solving a collection of problems concerning shortest paths and visibility withinP. These problems include calculation of the collection of all shortest paths insideP from a given source vertexS to all the other vertices ofP, calculation of the subpolygon ofP consisting of(More)
We show that a set of <i>n</i> points in the plane has at most <i>O</i>(10.05<sup><i>n</i></sup>) perfect matchings with crossing-free straight-line embedding. The expected number of perfect crossing-free matchings of a set of <i>n</i> points drawn i.i.d. from an arbitrary distribution in the plane is at most <i>O</i>(9.24<sup><i>n</i></sup>).Several(More)
We reexamine the notion of relative (p, ε)-approximations, recently introduced in [CKMS06], and establish upper bounds on their size, in general range spaces of finite VC-dimension, using the sampling theory developed in [LLS01] and in several earlier studies [Pol86, Hau92, Tal94]. We also survey the different notions of sampling, used in computational(More)
In this paper we give a new randomized incremental algorithm for the construction of planar Voronoi diagrams and Delaunay triangulations. The new algorithm is more “on-line” than earlier similar methods, takes expected timeO(nℝgn) and spaceO(n), and is eminently practical to implement. The analysis of the algorithm is also interesting in its own right and(More)
We consider the problem of computing the shortest path between two points in two- or three-dimensional space bounded by polyhedral surfaces. In the 2-D case the problem is easily solved in time <italic>O</italic>(<italic>n</italic><supscrpt>2</supscrpt> log <italic>n</italic>).In the general 3-D case the problem is quite hard to solve, and is not even(More)