# Pre-order traversal

## Steps

• Visit the root node
• traverse the left sub-tree in pre-order
• traverse the right sub-tree in pre-order

## Algorithm

• Step 1: Repeat Steps 2 to 4 while TREE != NULL
• Step 2: Write TREE -> DATA
• Step 3: PREORDER(TREE -> LEFT)
• Step 4: PREORDER(TREE -> RIGHT)
[END OF LOOP]
• Step 5: END

## C Function

### Example

Traverse the following binary tree by using pre-order traversal • Since, the traversal scheme, we are using is pre-order traversal, therefore, the first element to be printed is 18.
• traverse the left sub-tree recursively. The root node of the left sub-tree is 211, print it and move to left.
• Left is empty therefore print the right children and move to the right sub-tree of the root.
• 20 is the root of sub-tree therefore, print it and move to its left. Since left sub-tree is empty therefore move to the right and print the only element present there i.e. 190.
• Therefore, the printing sequence will be 18, 211, 90, 20, 190.

### Feedback   