伪代码

topologicalSort(n, edges):
   build directed adjacency; compute indeg[v] for all v
   order = []
   repeat n times:
      pick = smallest v with indeg[v] == 0 (none left -> stop)
      mark pick as used (indeg[pick] = -1)
      order.add(pick)
      for nb in adj[pick]:
         indeg[nb] -= 1
   return order