Abstract
Let P n be a set of n points on the plane in general position, n ≥ 4. A convex quadrangulation of P n is a partitioning of the convex hull \(\mathit{Conv}(P_n)\) of P n into a set of quadrilaterals such that their vertices are elements of P n , and no element of P n lies in the interior of any quadrilateral. It is straightforward to see that if P admits a quadrilaterization, its convex hull must have an even number of vertices. In [6] it was proved that if the convex hull of P n has an even number of points, then by adding at most \(\frac{3n}{2}\) Steiner points in the interior of its convex hull, we can always obtain a point set that admits a convex quadrangulation. The authors also show that \(\frac{n}{4}\) Steiner points are sometimes necessary. In this paper we show how to improve the upper and lower bounds of [6] to \(\frac{4n}{5}+2\) and to \(\frac{n}{3}\) respectively. In fact, in this paper we prove an upper bound of n, and with a long and unenlightening case analysis (over fifty cases!) we can improve the upper bound to \(\frac{4n}{5}+2\), for details see [9].
Supported by CONACYT of Mexico, Proyecto SEP-2004-Co1-45876, and PAPIIT (UNAM), Proyecto IN110802.
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Heredia, V.M., Urrutia, J. (2007). On Convex Quadrangulations of Point Sets on the Plane. In: Akiyama, J., Chen, W.Y.C., Kano, M., Li, X., Yu, Q. (eds) Discrete Geometry, Combinatorics and Graph Theory. CJCDGCGT 2005. Lecture Notes in Computer Science, vol 4381. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-70666-3_5
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DOI: https://doi.org/10.1007/978-3-540-70666-3_5
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