图的拓扑排序,是无前趋的接点拓扑排序,数据结构实验的同学可以看看!-map of topological sorting, and there is no contact before becoming the topological sorting, data structure experiments students can see!

实现拓扑排序算法，可用于判断图中是否存在环-Achieve topological sorting algorithm to determine the existence of maps Central