单源最短路径问题，分支限界法的优先队列解法，最小堆来存储活结点表，表示活结点优先队列，优先级是结点所对应的当前路长,Single-source shortest path problem, branch and bound method of the priority queue method, the smallest heap to store slipknot points table, said slipknot point priority queue, priority is the node corresponding to the current path length