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BinaryTree.java
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BinaryTree.java
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package com.aman.data_structures;
import com.sun.source.tree.Tree;
import javax.swing.tree.TreeNode;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
public class BinaryTree {
private TreeNode root;
private class TreeNode{
private TreeNode left;
private TreeNode right;
private int data; // Generic Type
public TreeNode(int data){
this.data = data;
}
}
public void createBinaryTree(){
TreeNode first = new TreeNode(9);
TreeNode second = new TreeNode(2);
TreeNode third = new TreeNode(3);
TreeNode fourth = new TreeNode(4);
root = first; // root ---> first
first.left = second;
first.right = third; // second <--- first ---> third
second.left = fourth;
// second.right = fifth; // fourth <--- second ---> fifth
}
public static void main(String[] args) {
BinaryTree bt = new BinaryTree();
bt.createBinaryTree();
// calling preOrder method
// bt.preOrder(bt.root); // recursive call
// bt.preOrder(); // iterative call
// calling inOrder method
// bt.inOrder(bt.root); // recursive call
// bt.inOrder(bt.root); // iterative call
// calling postOrder method
// bt.postOrder(bt.root); // recursive call
// bt.postOrder(); // iterative call
// calling levelOrder method
// bt.levelOrder();
// calling findMax method & printing the result
System.out.println(bt.findMax());
}
// recursive preorder traversal
// public void preOrder(TreeNode root){
// if(root == null){
// return;
// }
//
// System.out.print(root.data + " ");
// preOrder(root.left);
// preOrder(root.right);
// }
// iterative preorder traversal
public void preOrder(){
if(root == null){
return;
}
Stack<TreeNode> stack = new Stack<>();
stack.push(root);
while(!stack.isEmpty()){
TreeNode temp = stack.pop();
System.out.print(temp.data + " ");
if(temp.right != null){
stack.push(temp.right);
}
if(temp.left != null){
stack.push(temp.left);
}
}
}
// recursive inorder traversal
// public void inOrder(TreeNode root){
// if(root == null){
// return;
// }
//
// inOrder(root.left);
// System.out.print(root.data + " ");
// inOrder(root.right);
// }
// iterative inorder traversal
public void inOrder(TreeNode root){
if(root == null){
return;
}
Stack<TreeNode> stack = new Stack<>();
TreeNode temp = root;
while(!stack.isEmpty() || temp != null){
if(temp != null){
stack.push(temp);
temp = temp.left;
}
else{
temp = stack.pop();
System.out.print(temp.data + " ");
temp = temp.right;
}
}
}
// recursive postorder traversal
// public void postOrder(TreeNode root){
// if(root == null){
// return;
// }
//
// postOrder(root.left);
// postOrder(root.right);
// System.out.print(root.data + " ");
// }
// iterative postorder traversal
public void postOrder(){
TreeNode current = root;
Stack<TreeNode> stack = new Stack<>();
while(current != null || !stack.isEmpty()){
if(current != null){
stack.push(current);
current = current.left;
}
else{
TreeNode temp = stack.peek().right;
if(temp == null){
temp = stack.pop();
System.out.print(temp.data + " ");
while(!stack.isEmpty() && temp == stack.peek().right){
temp = stack.pop();
System.out.print(temp.data + "");
}
}
else{
current = temp;
}
}
}
}
// levelorder traversal
public void levelOrder(){
if(root == null){
return;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
while(!queue.isEmpty()){
TreeNode temp = queue.poll();
System.out.print(temp.data + " ");
if(temp.left != null){
queue.offer(temp.left);
}
if(temp.right != null){
queue.offer(temp.right);
}
}
}
// find maximum value in a Binary Tree
public int findMax(){
return findMax(root); // the root value is from the top where it was declared
}
public int findMax(TreeNode root){
if(root == null){
return Integer.MIN_VALUE;
}
int result = root.data;
int left = findMax(root.left);
int right = findMax(root.right);
if(left > result){
result = left;
}
if(right > result){
result = right;
}
return result;
}
}