This type of top down learning doesn't work for interviews. Just like how you can't learn math by reading high level summaries written by others. You have to

This type of top down learning doesn't work for interviews. Just like how you can't learn math by reading high level summaries written by others. You have to grind through it and see the connections yourself. The author's lack of depth shows when he says that no graph means you can rule out DFS. I also disagree on asking interviewer for the expected runtime. You're needlessly adding another constraint on yourself by doing that. You should ask for the input size and then figure out the best runtime that you can reach. A working suboptimal solution is more likely to get you to the next round than an incomplete attempt at an optimal solution.