Algorithm 9.1 DFS Input: A directed or undirected graph G=(V,E) Output: Preordering and postordering of the vertices in the corresponding depth first tree 1价++4tme<-0 2. for each vertex v∈V 3. mark v united +vpre <-intint 4. end for ost <--infiniti 5. for each vertex v∈V 6. if v is marked unvisited then dfs( Procedure dfsly 1. mark y visited time <--time oredfi-+-predfi +2<F- vpre <--time for each edge()∈E 4. if w is marked unvisited then dfs( w) 5. end for time <--time 6. posture postur+1 v post <--time 2/32021 Xiaojuan Caitime <-- time + 1 v.post <-- time time <-- time + 1 v.pre <-- time v.pre <-- infinity v.post <-- infinity time <-- 0 2/3/2021 Xiaojuan Cai 15