pipe

代码说明：

  某石油公司计划建造一条由东向西的主输油管道。该管道要穿过一个有n 口油井的油田。从每口油井都要有一条输油管道沿最短路经(或南或北)与主管道相连。如果给定n 口油井的位置,即它们的x 坐标（东西向）和y 坐标（南北向）,应如何确定主管道的最优位置, 即使各油井到主管道之间的输油管道长度总和最小的位置?证明可在线性时间内确定主管道的最优位置。(An oil company plans to construct a east to west from the main pipeline. The pipeline to pass through an oil field n wells. Wells from each must have a pipeline along the shortest path (or South or North) connected with the competent Road. If given the location of oil wells in n, that is, their x coordinates (east-west) and y coordinates (north-south), should be how to determine the optimal position in charge of Road, even if the wells to the pipeline in charge of Road between the sum of the smallest length location? proved to be linear time to determine the optimal position in charge of Road.)