Скачать или смотреть 31251 Lec 11.3: Topological Sort

In this video we go even deeper into depth-first search. We look at three orderings of vertices that can be produced by looking at when depth-first search starts and finishes exploring the vertex. These are 1) preorder, putting the vertices in order of starting times, 2) postorder, putting vertices in order of finishing time, and 3) reverse postorder, just the reverse of postorder. We show that in a directed acyclic graph reverse postorder gives a topological sort. The code to produce a topological sort of a DAG is thus again a simple addition to depth-first search.

Code to detect a cycle and if no cycle exists output a topological sort:
https://godbolt.org/z/Esa56YT4E