说明：  无向图应用问题 任务：如果以五向网表示n个城市之间通信网络的建设计划，顶点表示城市，边上的权表示该线路的造价，设计一个方案，使这个通讯网的总造价最低。 提示：这是一个求最小生成树的问题。n个城市名和各边的权值由用户输入，建立图的邻接矩阵，然后以Prim算法来求最小生成树，然后输出方案。
( The application of an undirected graph Task: If the five-way communications network, said network between n cities construction plan, the vertices represent cities, said the right side of the line cost, design a plan to make the lowest total cost of this communications network. Tip: This is a minimum spanning tree problem. n cities weights on each side of the name and entered by the user to establish the adjacency matrix, then Prim algorithm to find the minimum spanning tree, and then output the program.)