After McCallum and Avis [4] showed that the convex hull of a simple polygon P with n vertices can be constructed in O(n) time, several authors [1,2,3] devised simplified algorithms for this problem. Graham and Yao [2] presented a particularly simple and elegant one. After finding two points of the convex hull, their algorithm generated all other hull vertices using only one stack for intermedia...

We answer the question initially posed by Arik Tamir at the Fourth NYU Computational Geometry Day (March, 1987): “Given a collection of compact sets, can one decide in polynomial time whether there exists a convex body whose boundary intersects every set in the collection?” We prove that when the sets are segments in the plane, deciding existence of the convex stabber is NP-hard. The problem re...

The associahedron is a convex polytope whose vertices correspond to triangulations of a convex polygon. We define two signed or hyperoctahedral analogues of the associahedron, one of which is shown to be a simple convex polytope, and the other a regular CW-sphere.

We discovered the new tiling patterns each of which is composed of a single kind of convex pentagon. Moreover, we propose a new concept of classification method of the tessellating convex pentagons, which is the only unsolved case among the corresponding tessellating convex polygon problems.

Strong visibility is a generalization of standard visibility, defined with respect to a fixed set of line orientations. We investigate computational properties of this generalized visibility, as well as the related notion of strong convexity. In particular, we describe algorithms for the following tasks: 1. Testing the strong visibility of two points in a polygon and the strong convexity of a p...

In this paper we address several variants of the polygon an-nulus placement problem: given an input polygon P and a set S of points, nd an optimal placement of P that maximizes the number of points in S that fall in a certain annulus region deened by P and some ooset distance > 0. We address the following variants of the problem: placement of a convex polygon as well as a simple polygon; placem...

We devise dynamic algorithms for the following (weak) visibility polygon computation problems: • Maintaining visibility polygon of a fixed point located interior to simple polygon amid vertex insertions and deletions to simple polygon. • Answering visibility polygon query corresponding to any point located exterior to simple polygon amid vertex insertions and deletions to simple polygon. • Main...