Depth-first search time =0 pre/post W 1/12Q Z W 7/)8 V DES tree 2/32021 Xiaojuan Cai 12Depth-first search u w x y z u u u v v x y w z y x DFS tree w z time = 0 pre/post 1/ 2/ 3/ 4/5 10 11 12 6/ 7/8 9 2/3/2021 Xiaojuan Cai 12