说明：  图的遍历； 输入一个无向铁通讯网图，用Prim和Kruskal算法计算最小生成树并输出； 输入一个无向铁路交通图、始发站和终点站，用Dijkstra算法计算从始发站到终点站的最短路径。
(Traversal of graphs; Find the minimum cost spanning tree of communication network. Input an undirected railway traffic map, starting station and terminal, and use Dijkstra algorithm to calculate the shortest path from the starting station to the terminal.)