We consider the situation where one is given a set S of points in the plane and a collection D of unit disks embedded in the plane. We show that finding a minimum cardinality subset of D such that any path between any two points in S is intersected by at least one disk is NP-complete. This settles an open problem raised in . Using a similar reduction, we… (More)
Let S be a set of n points in the plane. We present data structures that solve range-aggregate query problems on three geometric extent measure problems. Using these data structures, we can report , for any axis-parallel query rectangle Q, the area/perimeter of the convex hull, the width, and the radius of the smallest enclosing disk of the points in S ∩ Q.
Given a polygon P , for two points s and t contained in the polygon, their geodesic distance is the length of the shortest st-path within P. A geodesic disk of radius r centered at a point v ∈ P is the set of points in P whose geo-desic distance to v is at most r. We present a polynomial time 2-approximation algorithm for finding a densest geodesic unit… (More)
We present an O(n log 2 n) time 2-approximation algorithm for computing the number of geodesic unit disks needed to cover the boundary of a simple polygon on n vertices. The running time thus only depends on the number of vertices and not on the number of disks; the disk centers can be computed in additional time proportional to the number of disks.