Depth First
Recursive
Tree Traversal

https://www.geeksforgeeks.org/tree-traversals-inorder-preorder-and-postorder/

Inorder
(Left, Root, Right) : 4 2 5 1 3
- Traverse the left subtree, i.e., call Inorder(left-subtree)
- Visit the root.
- Traverse the right subtree, i.e., call Inorder(right-subtree)
Preorder
(Root, Left, Right) : 1 2 4 5 3
- Visit the root.
- Traverse the left subtree, i.e., call Preorder(left-subtree)
- Traverse the right subtree, i.e., call Preorder(right-subtree)
Postorder
(Left, Right, Root) : 4 5 2 3 1
- Traverse the left subtree, i.e., call Postorder(left-subtree)
- Traverse the right subtree, i.e., call Postorder(right-subtree)
- Visit the root.