Binary Search Tree (BST) Traversals – Inorder, Preorder, Post Order

Given a Binary Search Tree, The task is to print the elements in inorder, preorder, and postorder traversal of the Binary Search Tree. 

Input: 

👁 Image

Output: 
Inorder Traversal: 10 20 30 100 150 200 300
Preorder Traversal: 100 20 10 30 200 150 300
Postorder Traversal: 10 30 20 150 300 200 100

Input: 

👁 Image

Output: 
Inorder Traversal: 8 12 20 22 25 30 40
Preorder Traversal: 22 12 8 20 30 25 40
Postorder Traversal: 8 20 12 25 40 30 22

Inorder Traversal:

Below is the idea to solve the problem:

At first traverse left subtree then visit the root and then traverse the right subtree.

Follow the below steps to implement the idea:

• Traverse left subtree
• Visit the root and print the data.
• Traverse the right subtree

The inorder traversal of the BST gives the values of the nodes in sorted order. To get the decreasing order visit the right, root, and left subtree.

Below is the implementation of the inorder traversal.

Inorder Traversal: 10 20 30 100 150 200 300 

Time complexity: O(N), Where N is the number of nodes.
Auxiliary Space: O(h), Where h is the height of tree

Preorder Traversal:

Below is the idea to solve the problem:

At first visit the root then traverse left subtree and then traverse the right subtree.

Follow the below steps to implement the idea:

• Visit the root and print the data.
• Traverse left subtree
• Traverse the right subtree

Below is the implementation of the preorder traversal.

Preorder Traversal: 100 20 10 30 200 150 300 

Time complexity: O(N), Where N is the number of nodes.
Auxiliary Space: O(H), Where H is the height of the tree

Postorder Traversal:

Below is the idea to solve the problem:

At first traverse left subtree then traverse the right subtree and then visit the root.

Follow the below steps to implement the idea:

• Traverse left subtree
• Traverse the right subtree
• Visit the root and print the data.

Below is the implementation of the postorder traversal:

PostOrder Traversal: 10 30 20 150 300 200 100 

Time complexity: O(N), Where N is the number of nodes.
Auxiliary Space: O(H), Where H is the height of the tree