代码的功能：用C语言仿真有向图的拓扑排序，代码中带有详细的注解，十分有利于阅读。拓扑排序算法是有向图的应用领域中的一种重要算法,阐述了AOV图的定义及拓扑排序算法思想。

-Functionality of the code: a directed graph topological sort in C language simulation code with detailed comments, very conducive to reading. The topological sort algorithm is to an important algorithm in Figure fields of application, on the AOV Graph definition and topological sorting algorithm thought.