说明：  链路状态路由算法实现。链路状态算法又叫最短路径优先SPF（Short Path First）算法。按照SPF的要求，路由器中路由表依赖于一张能表示整个个网络拓扑结构的无向图G（V，E）。
(Link state routing algorithm. Link State algorithm called the shortest path first SPF (Short Path First) algorithm. In accordance with the requirements of SPF, the router relies on a routing table can be said that the entire network topology undirected graph G (V, E).)