Give a counterexample to the conjecture that if a directed graph G contains a path from u to , then any depth-first search must result in v.d ≤ u.f.
Step 11 of 10
An idea would be to end a branch of a graph with and then go back to . That would give us , which is what we have to show.
We need not look any further for a counterexample, in fact, we only need to look back to a previous problem where we had the following search: