Introduction to Binary Trees - Advanced Topics in Java: Core Concepts in Data Structures - page 219

The pre-order traversal of this tree

A

C

B

is A B C .
The pre-order traversal of this tree

C

G

E

N

B A

F

J K

H

is C E F H B G A N J K .

This is in-order traversal :

1. Traverse the left subtree in in-order.

2. Visit the root.

3. Traverse the right subtree in in-order.

Here we traverse the left subtree first, then the root, and then the right subtree.
The in-order traversal of this tree

A

C

B

is B A C .
The in-order traversal of this tree

C

G

E

N

F B A

J K

H

is F H E B C A G J N K