package bst;

import java.util.Stack;

/** * Generic Binary Search Tree class. Implements Comparable Interface. * @author Bharat * * @param */public class BinarySearchTree { private Node root; public BinarySearchTree() { this.root = null; } /***************** Public Interfaces *****************/ /** * Recursive insert * @param data */ public void insert(T data) { root = insert(root, data); }

public void printPreOrder() { printPreOrder(root); }

public void printPostOrder() { printPostOrder(root); } public void printInOrder() { printInOrder(root); }

public void printPreOrderIterative() { printPreOrderIterative(root); }

public void printInOrderIterative() { printInOrderIterative(root); } public void printPostOrderIterative() { printPostOrderIterative(root); } /***************** Private Implementations *****************/ private Node insert(Node node, T data) { if (node == null) { node = new Node(data); } int compareResult = data.compareTo(node.getData());

if (compareResult < 0) { // If data < node's data Node newNode = insert(node.getLeft(), data); node.setLeft(newNode); } else if (compareResult > 0) { // If data > node's data Node newNode = insert(node.getRight(), data); node.setRight(newNode); } return node; } private void printPreOrder(Node root) { if (root == null) return; root.printValue(); printPreOrder(root.getLeft()); printPreOrder(root.getRight()); } private void printPostOrder(Node root) { if (root == null) return; printPostOrder(root.getLeft()); printPostOrder(root.getRight()); root.printValue(); } private void printInOrder(Node root) { if (root == null) return; printInOrder(root.getLeft()); root.printValue(); printInOrder(root.getRight()); } private void printPreOrderIterative(Node root) { Stack stack = new Stack(); stack.push(root); while (!stack.isEmpty()) { Node current = stack.pop(); current.printValue(); // Push the right node first since stack is LIFO. // We want left node to come out first. if (current.getRight() != null) stack.push(current.getRight()); if (current.getLeft() != null) stack.push(current.getLeft()); } } private void printInOrderIterative(Node root) { Stack stack = new Stack();

Node current = root; while (true) { // Keep pushing left node till hitting a null leaf if (current != null) { stack.push(current); current = current.getLeft(); } // Pop, print and go to right node else { if (stack.isEmpty()) return; current = stack.pop(); current.printValue(); current = current.getRight(); } } } private void printPostOrderIterative(Node root) { // Using 2 Stacks. Stack stack1 = new Stack(); Stack stack2 = new Stack(); Node current = root; stack1.push(current); while (!stack1.isEmpty()) { current = stack1.pop(); stack2.push(current); if (current.getLeft() != null) stack1.push(current.getLeft()); if (current.getRight() != null) stack1.push(current.getRight()); }

while (!stack2.isEmpty()) { current = stack2.pop(); current.printValue(); } } }