What Is Inorder in Data Structure?


Scott Campbell

What Is Inorder in Data Structure?

In the field of data structures, one common traversal technique is the inorder traversal. In this article, we will explore what inorder means and how it is used in various data structures.

Understanding Inorder

Inorder is a way to traverse or visit each node in a tree-like data structure such as a binary tree. It follows a specific order: left subtree, current node, right subtree.

This means that when performing an inorder traversal, we first visit the left subtree, then the current node, and finally the right subtree.

To better understand this concept, let’s consider an example of a binary tree:

       / \
      3   8
     / \   \
    1   4   10

When performing an inorder traversal on this tree, we would visit the nodes in the following order: 1, 3, 4, 5, 8, 10.

Applications of Inorder Traversal

Inorder traversal has various applications in data structures and algorithms. Some common use cases include:

  • Printing elements in ascending order: Inorder traversal allows us to print elements from a binary search tree in ascending order. As we visit nodes in a left-to-right manner, the elements are printed in their sorted order.
  • Expression evaluation: Infix expressions can be converted into postfix or prefix notation using an inorder traversal. This technique is often used to evaluate arithmetic expressions.
  • Creating sorted lists: By performing an inorder traversal on a binary search tree, we can create a sorted list of elements.

Implementing Inorder Traversal

To implement an inorder traversal algorithm, we can use recursion or iteration. Here’s an example of how it can be done recursively in Python:

def inorder_traversal(node):
    if node is not None:

In this recursive implementation, we first check if the current node is not None. If it is not, we recursively call the function on the left subtree, print the value of the current node, and then recursively call the function on the right subtree.


Inorder traversal is a fundamental technique in data structures that allows us to visit each node in a tree-like structure in a specific order. It has various applications ranging from printing elements in ascending order to expression evaluation.

By understanding and implementing inorder traversal, you will have a powerful tool in your programming arsenal.

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