How to Cover a Point Set with a V-Shape of Minimum Width

A balanced V-shape is a polygonal region in the plane contained in the union of two crossing equal-width strips. It is delimited by two pairs of parallel rays that emanate from two points x, y, are contained in the strip boundaries, and are mirror-symmetric with respect to the line xy. The width of a balanced V-shape is the width of the strips. We first present an O(n logn) time algorithm to compute, given a set of n points P , a minimum-width balanced V-shape covering P . We then describe a PTAS for computing a (1+ε)-approximation of this V-shape in time O((n/ε) logn+ (n/ε) log(1/ε)). A much simpler constant-factor approximation algorithm is also described.