文摘
Let P be a set of n points in . The 2-center problem for P is to find two congruent balls of minimum radius whose union covers P. We present a randomized algorithm for computing a 2-center of P that runs in expected time; here , is the radius of the 2-center balls of P, and is the radius of the smallest enclosing ball of P. The algorithm is near quadratic as long as is not too close to , which is equivalent to the condition that the centers of the two covering balls be not too close to each other. This improves an earlier slightly super-cubic algorithm of Agarwal, Efrat, and Sharir (2000) (at the cost of making the algorithm performance depend on the center separation of the covering balls).