Post Social Club Traversal Inwards Coffee Without Recursion - Illustration Tutorial

In the lastly article, I receive got shown yous how to implement post-order traversal inwards a binary tree using recursion too today I am going to learn yous close transportation service guild traversal without recursion. To live honest, the iterative algorithm of post-order traversal is the toughest with the iterative pre-order too in-order traversal algorithm. The procedure of post-order traversal remains the same but the algorithm to accomplish that lawsuit is different. Since post-order traversal is a depth-first algorithm, yous receive got to acquire deep earlier yous acquire wide. I mean, the left subtree is visited first, followed yesteryear correct subtree too finally the value of a node is printed. This is the argue why the value of root is printed lastly inwards the post-order traversal algorithm.

Now, let's encounter the utility of post-order traversal algorithm, what practise yous acquire from it too when practise yous purpose the post-order algorithm to traverse a binary tree? As oppose to inorder traversal which prints node of the binary search tree inwards sorted guild too tin terminate also live used to flatten a binary tree inwards the same guild it was created, post-order traversal tin terminate live used to inspect leaves earlier yous inspect root. It tin terminate also live used to generate a postfix sequence.

Now, 1 of the often asked questions is when practise yous purpose pre-order, post-order, or in-order traversal field dealing with binary tree information structure?

The full general betoken regarding usage of traversal algorithm is based on the requirement of your application similar if yous desire to inspect all roots earlier leaves use pre-order too if yous desire to inspect leaves earlier root too then purpose the post-order traversal algorithms, and  if yous desire to visit all nodes inwards the sorted order too then yous tin terminate use in-order traversal algorithm.


Good cognition of these primal binary tree algorithms is essential to operate yesteryear whatever coding interview too if haven't pass a proficient bargain of your fourth dimension inwards your schoolhouse too collages agreement these information construction fundamentals, I advise yous bring together the Data Structures too Algorithms: Deep Dive Using Java course on Udemy to larn to a greater extent than close non simply when to purpose pre-order, in-order, too post-order traversals, but also refresh all other primal information construction too algorithms.

Iterative Algorithm to implement transportation service guild traversal of Binary Tree

The recursive algorithm of transportation service guild traversal which nosotros receive got seen inwards the previous article was quite similar to recursive pre-order too recursive inwards order algorithms, all yous demand yous to practise was conform the guild of recursive business office telephone telephone to tally the guild on which left subtree, correct subtree, too root needs to traversed, but iterative algorithm of post-order traversal is rattling dissimilar than iterative pre-order too in-order traversal.

In fact, it's the most hard to implement with 3 traversal algorithm. Sure, yous notwithstanding purpose an explicitly Stack information construction to shop elements, but the backtracking too and then exploring correct subtree is a footling flake tricky to implement.

Here is 1 of the simplest post-order traversal algorithm without using recursion:

public void postOrderWithoutRecursion() {     Stack<TreeNode> nodes = new Stack<>();     nodes.push(root);      while (!nodes.isEmpty()) {       TreeNode electrical flow = nodes.peek();        if (current.isLeaf()) {         TreeNode node = nodes.pop();         System.out.printf("%s ", node.data);       } else {          if (current.right != null) {           nodes.push(current.right);           current.right = null;         }          if (current.left != null) {           nodes.push(current.left);           current.left = null;         }       }      }   }

If yous hold off at this method yous volition detect that we are examining leaves earlier examining root. We start the post-order traversal from the root yesteryear pushing it into a Stack too and then loop until our Stack is empty.

At each iteration, nosotros peek() the chemical component subdivision from Stack, I mean, nosotros recollect it without removing too depository fiscal establishment check if it's a leaf, if yeah too then nosotros pop() the chemical component subdivision too impress its value, which way the node is visited.

If it's non a leafage too then nosotros depository fiscal establishment check whether it has a correct node, if yeah nosotros shop into a tree too laid it to null, similarly, nosotros depository fiscal establishment check if it has left a node, if yeah nosotros force into the stack too and then score it null.

We starting fourth dimension insert correct node because Stack is a LIFO (last inwards starting fourth dimension out) information construction too every bit per post-order traversal nosotros demand to explore left subtree earlier correct subtree. If yous are non familiar with Stack (LIFO) too Queue (FIFO) information construction which is used inwards floor guild traversal, I advise yous accept a hold off at the Data Structure too Algorithms Specialization on Coursera 1 of the best resources to master copy this topic.

It's offered yesteryear the University of California too yous tin terminate access it for gratis if yous don't demand a certificate, but if yous need, perhaps to add together into your resume too LinkedIn profile, yesteryear all means, subscribe this specialization.

And, if yous similar a book,  simply read Introduction to Algorithms book yesteryear Thomas H. Cormen to larn to a greater extent than close essential information structures too algorithms.

Java Program for Binary tree PostOrder traversal

Here is our consummate Java programme to implement transportation service guild traversal of a binary tree inwards Java without using recursion. The iterative algorithm is encapsulated within the postOrder() method. We receive got used the same BinaryTree too TreeNode floor to implement a binary tree too and then added the postOrder() method to impress all nodes of a binary tree into transportation service order.

The algorithm nosotros receive got used doesn't demand recursion too it instead uses a field loop too a Stack, traditional tool to convert a recursive algorithm to an iterative one.

import java.util.Stack;  /*  * Java Program to traverse a binary tree   * using postOrder traversal without recursion.   * In postOrder traversal starting fourth dimension left subtree is visited,     followed yesteryear correct subtree  * too finally information of root or electrical flow node is printed.  *   * input:  * 55  * / \  * 35 65  * / \ \  * 25 45 75  * / / \  * xv 87 98  *   * output: xv 25 45 35 87 98 75 65 55   */  public class Main {    public static void main(String[] args) throws Exception {      // build the binary tree given inwards question     BinaryTree bt = BinaryTree.create();      // traversing binary tree on transportation service guild traversal without recursion     System.out         .println("printing nodes of binary tree on transportation service guild using iteration");     bt.postOrderWithoutRecursion();   }  }  class BinaryTree {   static class TreeNode {     String data;     TreeNode left, right;      TreeNode(String value) {       this.data = value;       left = correct = null;     }      boolean isLeaf() {       return left == nix ? correct == nix : false;     }    }    // root of binary tree   TreeNode root;    /**    * Java method to impress all nodes of tree inwards post-order traversal    */   public void postOrderWithoutRecursion() {     Stack<TreeNode> nodes = new Stack<>();     nodes.push(root);      while (!nodes.isEmpty()) {       TreeNode electrical flow = nodes.peek();        if (current.isLeaf()) {         TreeNode node = nodes.pop();         System.out.printf("%s ", node.data);       } else {          if (current.right != null) {           nodes.push(current.right);           current.right = null;         }          if (current.left != null) {           nodes.push(current.left);           current.left = null;         }       }      }   }    /**    * Java method to practise binary tree with seek information    *     * @return a sample binary tree for testing    */   public static BinaryTree create() {     BinaryTree tree = new BinaryTree();     TreeNode root = new TreeNode("55");     tree.root = root;     tree.root.left = new TreeNode("35");     tree.root.left.left = new TreeNode("25");     tree.root.left.left.left = new TreeNode("15");      tree.root.left.right = new TreeNode("45");     tree.root.right = new TreeNode("65");     tree.root.right.right = new TreeNode("75");     tree.root.right.right.left = new TreeNode("87");     tree.root.right.right.right = new TreeNode("98");      return tree;   }  }

When yous volition run this programme inwards your favorite IDE e.g. Eclipse or IntelliJIDea, yous volition encounter the next output:

Output printing nodes of a binary tree on transportation service guild using iteration 15 25 45 35 87 98 75 65 55 

You tin terminate encounter that nodes are printed inwards the transportation service order. You tin terminate also encounter the value of the root node is printed last.

list) 

Java Program to traverse a binary tree inwards pre-order without recursion (program)

How to impress all leafage nodes of a binary tree inwards Java? (solution) 

Java Program to impress leafage nodes of a binary tree without recursion? (program)

10 Algorithms Courses to Crack Coding Interviews (courses)

How to impress all leafage nodes of a binary tree without recursion inwards Java? (solution) 

How to implement a linked listing using generic inwards Java? (solution) 

How to contrary a singly linked listing inwards Java? (solution) 

How to traverse a binary tree inwards pre-order without using recursion? (solution) 

50+ Data Structure Problems from Coding Interview (questions)

10 (Free) Data Structure too Algorithms Courses for Devs (courses)

How to detect the third chemical component subdivision from the halt of a linked listing inwards Java? (solution)

How to contrary an array inwards house inwards Java? (solution) 

How to detect the middle chemical component subdivision of linked listing using a unmarried pass? (solution) 

Java programme to implement binary search using recursion? (solution) 

10 Data Structure Books Every Programmer Should Read (books)

How to impress duplicate elements of an array inwards Java? (solution)

Top 10 Courses to Learn Data Structure too Algorithms inwards Java (courses)

20 String Problems from Coding Interviews (question)

Thanks for reading this article thence far. If yous similar this tutorial too interview enquiry too then delight portion with your friends too colleagues. If yous receive got whatever feedback or enquiry too then delight driblet a comment too I'll endeavour to response your query.

P.S. - If yous don't hear learning from gratis resources too then yous tin terminate also accept a hold off at my listing of free information construction too algorithm courses for Java developers.