A non-empty binary tree is traversed in 3 types, namely pre-order, in-order and post-order in a recursive fashion.

Pre-order:

Pre-order process is as follows:

- Visit the root node

- Traverse the left sub tree

- Traverse the right sub tree

In-Order:

In order process is as follows:

- Traverse the left sub tree

- Visit the root node

- Traverse the right sub tree