Tree Traversals

Traversing A Binary Tree

• Traversing a binary tree is the process of visiting each and every node in the tree exactly once in a systematic way.
• As we know that a tree is a non-linear data structure in which the elements can be traversed in many different ways.
• Types of traversals

1. Pre-order Traversal
2. In-order Traversal
3. Post-order Traversal

Pre-order Traversal:-

• To traverse a nonempty binary tree in pre-order, the following operations are performed at each node:

1. Visiting the root node,
2. Traversing the left sub-tree,
3. Traversing the right sub-tree.

Pre-order Traversal: 1 2 4 3 5 7 8 6

• The pre-order traversal of the above tree is 1–2–4–3–5–7–8–6 as we have to traverse from root first, and then left sub-tree, and finally right sub-tree.
• Pre-order traversal is also called depth-first traversal.
• The word ‘pre’ in the pre-order specifies that the root node is traversed first to any other nodes in the left and right sub-trees.

C++ code for pre-order traversal

//recursive function to perform pre-order traversal of the tree

void preorder(struct node *root)

{

//if the current node is empty

if(root==NULL)

return;

//display the data part of the root node.

cout<<root->data;

//traverse the left sub-tree

preorder(root->left);

//traverse the right sub-tree

preorder(root->right);

}

In-order Traversal:

• To traverse a nonempty binary tree in in-order, the following operations are performed at each node:

1. Traversing the left sub-tree,
2. Visiting the root node,
3. Traversing the right sub-tree.

In-order Traversal: 4 2 1 7 5 8 3 6

• The in-order traversal of the above tree is 4–2–1–7–5–8–3–6.
• Left sub-tree first, and then root node, and finally the right sub-tree.
• In-order traversal is also called symmetric traversal.
• The word ‘in’ in the in-order…

Learn more