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.peh←0.potn←0 2. for each vertex v∈V 3. mark y unvisited 4. end for 5. for each vertex v∈V 6. if v is marked unvisited then dfs(v) Procedure dfsly 1. mark y visited 2. preen←- preen+1 for each edge()∈E 4. if w is marked unvisited then dfs( w) 5. end for 6. postdfn 4pastdfn +1 2/32021 Xiaojuan Cai 142/3/2021 Xiaojuan Cai 14