关于图的代码，可以实现最小生成树迪杰斯特拉算法等很多功能-Code on the map, you can implement lots such as Dijkstra algorithm of minimum spanning tree function

简单易懂的普利姆法求最小生成树的代码，新手可参考(Plymmerm easy to understand minimum spanning tree code, novice can refer to this code)