若要在n个城市之间建立通信网络，只需要架设n-1条线路即可。如何以最低的经济代价建设这个通信网，是一个网的最小生成树问题-To establish communication networks between n cities, only need to set up the n-1 lines can be. The lowest economic cost of construction communication network is a network of minimum spanning tree problem