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The Fréchet distance is a well studied and very popular measure of similarity of two curves. The best known algorithms have quadratic time complexity, which has recently been shown to be optimal assuming the Strong Exponential Time Hypothesis (SETH) [Bringmann, FOCS'14]. To overcome the worst-case quadratic time barrier, restricted classes of curves have been studied that attempt to capture realistic input curves. The most popular such class are -packed curves, for which the Fréchet distance has a -approximation in time [Driemel et al., DCG'12]. In dimension this cannot be improved to for any unless SETH fails [Bringmann, FOCS'14]. In this paper, exploiting properties that prevent stronger lower bounds, we present an improved algorithm with time complexity . This improves upon the algorithm by Driemel et al. for any . Moreover, our algorithm's dependence on , and is optimal in high dimensions apart from lower order factors, unless SETH fails. Our main new ingredients are as follows: For filling the classical free-space diagram we project short subcurves onto a line, which yields one-dimensional separated curves with roughly the same pairwise distances between vertices. Then we tackle this special case in near-linear time by carefully extending a greedy algorithm for the Fréchet distance of one-dimensional separated curves. [ABSTRACT FROM AUTHOR]

A variation on the classical polygon illumination problem was introduced in [Aichholzer et al. EuroCG'09]. In this variant light sources are replaced by wireless devices called -modems, which can penetrate a fixed number , of 'walls'. A point in the interior of a polygon is 'illuminated' by a -modem if the line segment joining them intersects at most edges of the polygon. It is easy to construct polygons of vertices where the number of -modems required to illuminate all interior points is . However, no non-trivial upper bound is known. In this paper we prove that the number of kmodems required to illuminate any polygon of vertices is . For the cases of illuminating an orthogonal polygon or a set of disjoint orthogonal segments, we give a tighter bound of . Moreover, we present an time algorithm to achieve this bound. [ABSTRACT FROM AUTHOR]