图的遍历:图是由顶点集合(vertex)及顶点间的关系集合组成的一种数据结构:Graph＝( V, E ).使用拓扑排序的算法.-traverse the map : The map is set by the vertex (Vertex) and the relationship between peak set consisting of a data structure : Graph = (V, E). The use of topological sorting algorithm.