منابع مشابه
On point covers of c-oriented polygons
Let S be any family of n c-oriented polygons of the two-dimensional Euclidean plane E, i.e., bounded intersection of halfplanes whose normal directions of edges belong to a .xed collection of c distinct directions. Let (S) denote the packing number of S, that is the maximum number of pairwise disjoint objects of S. Let (S) be the transversal number of S, that is the minimum number of points req...
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Let R and B be disjoint point sets such that R ∪ B is in general position. We say that B is enclosed by R if there is a simple polygon P with vertex set R such that all the elements in B belong to the interior of P . In this paper we prove that if the vertices of the convex hull of R ∪B belong to B, and |R| ≤ |Conv(R)| − 1 then B encloses R. The bound is tight. This improves on results of a pre...
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By a polygonization of a finite point set S in the plane we understand a simple polygon having S as the set of its vertices. Let B and R be sets of blue and red points, respectively, in the plane such that B ∪ R is in general position, and the convex hull of B contains k interior blue points and l interior red points. Hurtado et al. found sufficient conditions for the existence of a blue polygo...
متن کاملOn Polygons Enclosing Point Sets II
Let R and B be disjoint point sets such that R ∪ B is in general position. We say that B encloses by R if there is a simple polygon P with vertex set B such that all the elements in R belong to the interior of P . In this paper we prove that if the vertices of the convex hull of R ∪ B belong to B, and |R| ≤ |Conv(B)| − 1 then B encloses R. The bound is tight. This improves on results of a previ...
متن کاملCovers of Point-Hyperplane Graphs
A cover of the non-incident point-hyperplane graph of projective dimension 3 for fields of characteristic 2 is constructed. For fields F of even order larger than 2, this leads to an elementary construction of the non-split extension of SL4(F) by F6.
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ژورنال
عنوان ژورنال: Theoretical Computer Science
سال: 2001
ISSN: 0304-3975
DOI: 10.1016/s0304-3975(00)00227-9