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Traversals and Depth of Binary Tree
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‎README.md

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| ✅ | [Iterative Preorder Traversal](https://leetcode.com/problems/binary-tree-preorder-traversal/) | [Approach](#iterative-preorder-traversal) | [Java Soultion](./src/sde_sheet/.java) |
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| ✅ | [Iterative Postorder Traversal (Using 2 stacks)](https://leetcode.com/problems/binary-tree-postorder-traversal/) | [Approach](#using-2-stacks) | [Java Soultion](./src/sde_sheet/.java) |
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| ✅ | [Iterative Postorder Traversal (Using 1 stack)](https://leetcode.com/problems/binary-tree-postorder-traversal/) | [Approach](#using-1-stack) | [Java Soultion](./src/sde_sheet/.java) |
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| 🔃 | [All Traversals in one code](https://leetcode.com/problems/binary-tree-postorder-traversal/) | [Approach](#) | [Java Soultion](./src/sde_sheet/.java) |
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| 🔃 | [All Traversals in one code](https://leetcode.com/problems/binary-tree-postorder-traversal/) | [Approach](#preorder-inorder-postorder-traversals-in-one-traversal) | [Java Soultion](./src/sde_sheet/.java) |
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| 🔃 | [Binary Tree Right Side View](https://leetcode.com/problems/binary-tree-right-side-view/) | [Brute, Better & Optimal Approaches](#) | [Java Soultion](./src/sde_sheet/.java) |
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| 🔃 | [Bottom View of Binary Tree](https://practice.geeksforgeeks.org/problems/bottom-view-of-binary-tree/1#) | [Brute, Better & Optimal Approaches](#) | [Java Soultion](./src/sde_sheet/.java) |
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| 🔃 | [Top View of Binary Tree](https://practice.geeksforgeeks.org/problems/top-view-of-binary-tree/1) | [Brute, Better & Optimal Approaches](#) | [Java Soultion](./src/sde_sheet/.java) |
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<img src="assets/Iterative postorder traversal using 1 stack dry run 2.jpg" alt="Iterative postorder traversal using 1 stack dry run 2" width="400px" />
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## Preorder Inorder Postorder Traversals in One Traversal
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-
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---
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---

‎src/dsa_one/HeightOfBinaryTree.java

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public class HeightOfBinaryTree {
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public static int heightOfBinaryTree(Node root) {
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if (root == null)
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return 0;
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// Here we take the maximum height of left subtree and right subtree
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// Then we add one for counting the root for the height
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return Math.max(heightOfBinaryTree(root.left), heightOfBinaryTree(root.right)) + 1;
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}
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static Scanner sc = null;
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public static void main(String[] args) {
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}
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public static int heightOfBinaryTree(Node root) {
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if (root == null)
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return 0;
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return Math.max(heightOfBinaryTree(root.left), heightOfBinaryTree(root.right)) + 1;
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}
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static Node createTree() {
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Node root = null;

‎src/sde_sheet/DepthOfBinaryTree.java

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package sde_sheet;
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import java.util.Scanner;
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import tree_implementations.Node;
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public class DepthOfBinaryTree {
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public static int depthOfBinaryTree(Node root) {
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if (root == null)
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return 0;
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// Here we take the maximum height of left subtree and right subtree
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// Then we add one for counting the root for the height
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return Math.max(depthOfBinaryTree(root.left), depthOfBinaryTree(root.right)) + 1;
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}
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static Scanner sc = null;
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public static void main(String[] args) {
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sc = new Scanner(System.in);
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Node root = createTree();
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System.out.println("Height of the tree: " + depthOfBinaryTree(root));
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}
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static Node createTree() {
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Node root = null;
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System.out.println("Enter data: ");
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int data = sc.nextInt();
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if (data == -1)
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return null;
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root = new Node(data);
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System.out.println("Enter left for " + data);
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root.left = createTree();
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System.out.println("Enter right for " + data);
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root.right = createTree();
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return root;
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}
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}

‎src/sde_sheet/PreInPostOrderTraversals.java

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package sde_sheet;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Scanner;
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import java.util.Stack;
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import tree_implementations.Node;
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/*
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* Time Complexity: O(N)
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* where N is the no. of nodes in the tree
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* Space Complexity: O(N)
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* where N is the no. of nodes in the tree
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* (don't take the space of answer DS into account)
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*/
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class Pair {
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Node node;
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int num;
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Pair(Node _node, int _num) {
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num = _num;
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node = _node;
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}
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}
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class Answer {
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List<Integer> pre;
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List<Integer> in;
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List<Integer> post;
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Answer(List<Integer> _pre, List<Integer> _in, List<Integer> _post) {
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pre = _pre;
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in = _in;
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post = _post;
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}
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}
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public class PreInPostOrderTraversals {
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public static Answer preInPostOrderTraversals(Node root) {
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Stack<Pair> stack = new Stack<Pair>();
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stack.push(new Pair(root, 1));
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List<Integer> preOrder = new ArrayList<>();
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List<Integer> inOrder = new ArrayList<>();
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List<Integer> postOrder = new ArrayList<>();
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if (root == null)
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return null;
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while (!stack.isEmpty()) {
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Pair it = stack.pop();
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// this is part of pre order
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// increment 1 or 2
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// push the left side of the tree
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if (it.num == 1) {
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preOrder.add(it.node.data);
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it.num++;
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stack.push(it);
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if (it.node.left != null) {
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stack.push(new Pair(it.node.left, 1));
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}
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}
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// this is a part of in order
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// increment 2 to 3
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// push right
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else if (it.num == 2) {
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inOrder.add(it.node.data);
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it.num++;
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stack.push(it);
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if (it.node.right != null) {
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stack.push(new Pair(it.node.right, 1));
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}
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}
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// don't push it back again
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else {
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postOrder.add(it.node.data);
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}
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}
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// Only for Eclipse
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return new Answer(preOrder, inOrder, postOrder);
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}
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static Scanner sc = null;
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public static void main(String[] args) {
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sc = new Scanner(System.in);
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Node root = createTree();
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Answer ans = preInPostOrderTraversals(root);
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System.out.print("Preorder: ");
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for (int data : ans.pre) {
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System.out.print(data + ", ");
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}
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System.out.print("Inorder: ");
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for (int data : ans.in) {
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System.out.print(data + ", ");
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}
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System.out.print("Postorder: ");
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for (int data : ans.post) {
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System.out.print(data + ", ");
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}
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}
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static Node createTree() {
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Node root = null;
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System.out.println("Enter data: ");
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int data = sc.nextInt();
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if (data == -1)
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return null;
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root = new Node(data);
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System.out.println("Enter left for " + data);
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root.left = createTree();
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System.out.println("Enter right for " + data);
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root.right = createTree();
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return root;
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}
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}
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/*
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* Example 1:
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1
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-1
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Preorder: 1, 2, 3, 4, 5, 6, 7, Inorder: 3, 2, 4, 1, 6, 5, 7, Postorder: 3, 4, 2, 6, 7, 5, 1,
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*/

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