Postorder Tree Traversal In Binary Tree In C++

March 2, 2023

Postorder Tree Traversal

Postorder traversal is a depth first algorithm. There are three types of traversals in tree: Preorder, Inorder, Postorder. In this article, postorder tree traversal is performed using recursion.

Postorder tree traversal in binary tree in Cpp

More About Postorder Traversal:

  1. In postorder traversal, we first move to the left subtree then to the right subtree and finally print the node.
  2. Used when we want to free the nodes of the tree.
  3. It is also used to find the postfix expression.
postorder-tree-traversal-in-binary-tree

Steps To Find Postorder Traversal:

  1. Traverse the left subtree. Print the leftmost node ie 5.
  2. Move back, traverse the right subtree.
  3. Since there is no right subtree, 8 is printed.
  4. 13 is printed and the parent node is printed which is 12.
  5. Finally move, to the right subtree.
  6. 18 and 54 are printed.
  7. Print the root.

 

Postorder tree traversal in binary tree in Cpp
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Trees in Data Structure(Introduction)

Types of Trees in data structure

Inorder Postorder Preorder Traversal Examples

Inorder Tree Traversal in Binary Tree

Preorder Tree Traversal in Binary Tree

Algorithm To Find Postorder Traversal:

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

Code Implementation for Preorder 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 postorder_traversal (Tree * root)
{
  if (root == NULL)
    return;
  // Visit Left subtree
  postorder_traversal (root->left);
  // Visit right subtree
  postorder_traversal (root->right);
  // Print the data
  cout << root->data << " ";
}

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);
  postorder_traversal (root);
  return 0;
}


Output:

5 8 13 12 18 54 15

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