邮局选址

问题描述：在一个按照东西和南北方向划分成规整街区的城市里，n个居民点散乱地分布在不同的街区中。用x坐标表示东西向，用y坐标表示南北向。各居民点的位置可以由坐标(x,y)表示。要求：为建邮局选址，使得n个居民点到邮局之距离的总和最小。

提示：带权中位数（分治算法）

-Post office location problem descr iption: a north-south direction and in accordance with what is divided into regular city blocks, n scattered settlements located in different neighborhoods. Showing something to coordinate with x, y coordinates used to represent the north and south. Positions of settlements can be represented by the coordinates (x, y). Requirements: In order to build the post office location, so that the n settlements　the post office to the sum of the minimum. Tip: weighted median (divide and conquer algorithm)