本作业为邮局选址问题。在该问题中，求邮局的最佳位置即求坐标的中位数。分解来看，即分别寻找X和Y坐标的中位数。

类设计如下：设计一个PostCal的类。计算X,Y坐标的中位数方法selectMedian()，其中partition()用于将大问题分解为子问题使用。最后有一个计算邮局到各居民点的路径总和int calSum()。

类中包含构造函数PostCal()，主要功能是实现文件读写，结果计算及输入输出。

类中包含取居民点个数的变量 num。-This job is a post office location problem. In this issue, find the best location for the post office that is seeking the median coordinates. Decomposition point of view, the X and Y coordinates, respectively, find the median.

Class is designed as follows: Design a PostCal category. Calculate X, Y coordinates of the median method selectMedian (), which partition () is used to a large problem into sub-problems to use. Finally there is a post office to calculate the sum of each path of settlements int calSum ().

       　Class contains a constructor PostCal (), the main function is to implement file read and write, calculate and input and output results.

       　Class contains the number of variables to take settlements num.