Suppose we perform Depth First Search $($DFS$)$ on a digraph G$=($V$,$E$)$

given by its adjacency list structure and label each node u in V

by d$[$u$]$

and f$[$u$]$

$,$ indicating the starting and finishing times of DFSvisit$($u$),$ as we learned in the course.

Consider an arbitrary pair of distinct vertices u

and v

such that there is a directed path from u

to v

in G

$.$ Then that implies