说明：  1.必须完成图的存储功能。图的输入可由命令行完成； 2.按遍历到的先后顺序依次输出G中各结点内容； 3.以文本形式输出生成树中各条边以及它们的权值。
(1. Must complete map of the storage function. Map the input command line can be completed 2. According to the order traversal order of the output G of the contents of each node 3. As text output in the spanning tree edges and their weights.)