Inorder Tree Traversal in Binary Tree In C++

August 8, 2025

Inorder Tree Traversal

Inorder Traversal in Binary Tree in C++ – Inorder traversal is a common method to visit all nodes in a binary tree. It follows the Left → Root → Right order. This means we first visit the left subtree, then the root node, and finally the right subtree. In a Binary Search Tree (BST), this gives us the values in sorted order.

In this blog, we’ll see how to implement Inorder Traversal in C++ with easy examples and clear explanations. Inorder traversal is a depth first algorithm. There are three types of traversals in tree: Preorder, Inorder, Postorder. In this article, inorder tree traversal is performed using recursion.

Inorder Tree Traversal In Binary Tree in C++ language

Inorder Tree Traversal in Binary Tree in C++

Inorder traversal is a type of depth-first traversal where the nodes are visited in the following order:
first the left subtree, then the root node, and finally the right subtree.

Steps To Find Inorder Traversal:

  1.  Leftmost node is 5 so print 5
  2.  Move back, print 8 and look for right child.
  3.  As there is no right child, print 12 and move to the right subtree.
  4. 13 is printed and whole subtree is covered.
  5. Print 15 and move to the right subtree.
  6. 18 and 54 are printed and tree is covered.
Inorder Tree traversal in binary tree in cpp

What is Inorder generally used for?

We generally use Inorder traversal technique on Binary Tress , as it fetches the values from the underlying set in order. Using Post-order traversal is also an option, but during post order traversal while delete or freeing nodes it can even delete or free an entire binary tree, which is not a favorable condition.

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Trees in Data Structure(Introduction)

Types of Trees in data structure

Inorder Postorder Preorder Traversal Examples

Preorder Tree Traversal in Binary Tree

Postorder Tree Traversal in Binary Tree

Algorithm To Find Inorder Traversal:

  1. If root is NULL, return NULL.
  2. Visit the left subtree.
  3. Print the node.
  4. Visit the right subtree.

Code Implementation for Inorder Tree traversal

Run 
#include<bits/stdc++.h>
using namespace std;
class Tree
{
public:
  int data;
  Tree *left = NULL, *right = NULL;
  // Constructor initialised
    Tree (int x)
  {
    data = x;
    left = NULL;
    right = NULL;
  }
};
void inorder_traversal (Tree * root)
{
  if (root == NULL)
    return;
  // Visit Left subtree
  inorder_traversal (root->left);
  // Print the data
  cout << root->data << " ";
  // Print the right subtree
  inorder_traversal (root->right);
}

int main ()
{
  Tree *root = new Tree (15);
  root->left = new Tree (12);
  root->right = new Tree (54);
  root->left->left = new Tree (8);
  root->left->right = new Tree (13);
  root->left->left->left = new Tree (5);
  root->right->left = new Tree (18);
  inorder_traversal (root);
  return 0;
}


Output:
5 8 12 13 15 18 54

Conclusion

Inorder traversal is one of the most important and commonly used methods to go through a binary tree, especially when dealing with Binary Search Trees. It helps in visiting nodes in a sorted manner, first the left child, then the root, and finally the right child. Whether you use recursion or iteration, understanding how Inorder traversal works builds a strong foundation for solving many tree-related problems in C++.

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FAQs - Inorder Tree Traversal in Binary Tree In C++

FAQs - Inorder Tree Traversal in Binary Tree In C++

Inorder traversal alone cannot uniquely reconstruct a binary tree because it does not provide enough information about the tree structure. However, if combined with either preorder or postorder traversal, the original binary tree can be reconstructed.

  • Recursive Inorder Traversal has a time complexity of O(n) and space complexity of O(h), where h is the height of the tree (due to call stack usage).
  • Iterative Inorder Traversal using a stack also takes O(n) time and O(h) space for the stack.

In a valid BST, the Inorder traversal should produce values in strictly increasing order. If the sequence is not sorted or has duplicates (when not allowed), the tree is not a valid BST.

Morris Inorder Traversal is an advanced method that performs traversal without using a stack or recursion. It uses a concept called threaded binary trees and modifies tree links temporarily to achieve O(1) space complexity. However, it’s more complex and not typically used in basic scenarios.

Inorder traversal is best suited for Binary Search Trees where sorted output is useful. However, in general binary trees, it may not provide meaningful node processing order depending on the problem. For tasks like serialization or hierarchy-based processing, preorder or level-order might be more appropriate.

This is possible through Morris Traversal, which temporarily modifies the tree structure by creating links to predecessors and restores it after traversal. It’s tricky to implement but avoids extra memory usage, making it space-efficient.

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