To search in a graph, we first build a tree covering the graph.
Breadth first search
BFS browse by increasing depth to the root.
In-depth search: pre-order
In-depth algorithms are recursive. In the prefix path, we always browse the left subtree before processing the right subtree.
In-depth search: in-order
The LNR browse as far left as possible, and display the branches from left to right. This algorithm display the diagonals from bottom to top.
In-depth search: out-order
This is a diagonal browsing from top to bottom.