"I'm familiar with the meaning of this question. There are a couple of ways to answer it, so I will give you both examples. The two most common methods of searching a graph or a tree related to a depth-first search are depth-first search and breadth-first search, for starters. Depending on the application you are using and the result you want to achieve, this should be determined by the type of data in your tree or graph data structure. For a Breath First Search, I start at the root node. I then search all their children nodes moving from left to right, then I repeat the process at the level below the root node. I typically repeat this on each level until I reach the end of the tree or node. As a general practice, I use a queue as an intermediary step as a way of keeping track of what nodes I need to search."