prim算法是从连通网中的某一个顶点开始，以此作为生成树的初始状态，然后不断的将网中的其他顶点添加到生成树上，直到最后一个顶点添加到生成数上时得到最小生成树．-prim algorithm is network connectivity from a vertex to start, as a spanning tree of the initial state, and then continuing to network other vertex added to the spanning