Introduction to Binary Trees - Advanced Topics in Java: Core Concepts in Data Structures - page 220

This is post-order traversal :

1. Traverse the left subtree in post-order.

2. Traverse the right subtree in post-order.

3. Visit the root.

Here we traverse the left and right subtrees before visiting the root.
The post-order traversal of this tree

A

C

B

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

C

E G

N

B A

F

K

J

H

is H F B E A J K N G C .
Note that the traversals derive their names from the place where we visit the root relative to the traversal of
the left and right subtrees. As another example, consider a binary tree that can represent the following arithmetic
expression:

(54 + 37) / (72 - 5 * 13)

Here is the tree:

/

+ -

54 37 72 *

5 13

The leaves of the tree contain the operands, and the branch nodes contain the operators. Given a node
containing an operator, the left subtree represents the first operand, and the right subtree represents the second
operand.
The pre-order traversal is: / + 54 37 - 72 * 5 13
The in-order traversal is: 54 + 37 / 72 - 5 * 13
The post-order traversal is: 54 37 + 72 5 13 * - /