Ch5 DFS - Bootstrap your algorithms.

As we all know BFS and DFS are the famous two pillars of the Searching algorithms.

Now as we all know BFS can be easily accomplished with a simple Queue. Or let's say a FIFO data structure.

But the DFS remains a tricky one, for we actually usually keep the main function concise and just call a beefy helper function to get it done.

Of course somebody will raise their hand and say "Why not just use recursion?"
Baby, recursion and iterations are not algorithms themselves, however they remains two different styles of implementing the same algorithms.

Now talk is cheap, show me the code: