Ch4 BFS - Bootstrap your algorithms.

Now as it is known to all, the BFS can be easily implemented with the help of a Queue, or more so a FIFO data structure.

But much less known to all, the BFS has quite a few variations of implementation.
For starters, there's two Queue implementation and there's one Queue.
You can use a level counter, or you can simply use a dummyNode.

Alright so here's just one way of going about doing it.

PS: If you are using Java 8 and love succinct code, just use offer and poll methods as they don't invoke type conversion like the addFirst, addLast do. Which can look quite unappreciated.