n个社区之间的交通图用有向加权图来表示，现在要从这n个社区中选择一个社区建一所医院，问这所医院应建在哪个社区？能使所有的社区医院都比较近，能使您医院最远的社区到医院最近，或能使所有的社区到大医院的距离之和达到最小。(The traffic map between the N communities is represented by a directed weighted map. Now, a community is selected from one of the N communities to build a hospital. In which community should the hospital be built? It can make all community hospitals close to the nearest community to the hospital or minimize the distance from all the communities to the large hospitals.)