通过鼠标点击界面，绘制一个图结构，用图论中的知识判断图的连通性，判断他是不是一棵树，另外还可以显示它的邻接矩阵、可达性矩阵等。-By mouse click interface, draw a graph structure, using graph theory knowledge to assess the graphs to determine that he is not a tree, it also can display the adjacency matrix, reachabi