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| package com.chung;
import java.util.LinkedList;
import java.util.Queue;
import node.*;
public class AVLTree {
BinaryNode root;
public BinaryNode getRoot() {
return root;
}
// Constructor
AVLTree() {
root = null;
}
// Insert values in AVL Tree
void insert(int value) {
root = insert(root, value);
}// end of method
// Helper Method
BinaryNode insert(BinaryNode currentNode, int value) {
// THIS ELSE_IF BLOCK IS BST CONDITION
if (currentNode == null) {
System.out.println("Successfully inserted " + value + " in AVL Tree");
return createNewNode(value);
} else if (value <= currentNode.getValue()) {
currentNode.setLeft(insert(currentNode.getLeft(), value));
} else {
currentNode.setRight(insert(currentNode.getRight(), value));
}
// THIS IS WHERE WE WILL DO AVL SPECIFIC WORK
int balance = checkBalance(currentNode.getLeft(), currentNode.getRight());
if (balance > 1) {
if (checkBalance(currentNode.getLeft().getLeft(), currentNode.getLeft().getRight()) > 0) {
currentNode = rightRotate(currentNode);// LL Condition
} else {
currentNode.setLeft(leftRotate(currentNode.getLeft())); // LR Condition
currentNode = rightRotate(currentNode);
}
} else if (balance < -1) {
if (checkBalance(currentNode.getRight().getRight(), currentNode.getRight().getLeft()) > 0) {
currentNode = leftRotate(currentNode);// RR Condition
} else {
currentNode.setRight(rightRotate(currentNode.getRight()));// RL Condition
currentNode = leftRotate(currentNode);
}
}
if (currentNode.getLeft() != null) {
currentNode.getLeft().setHeight(calculateHeight(currentNode.getLeft()));
}
if (currentNode.getRight() != null) {
currentNode.getRight().setHeight(calculateHeight(currentNode.getRight()));
}
currentNode.setHeight(calculateHeight(currentNode));
return currentNode;
}// end of method
// Helper Method
private BinaryNode leftRotate(BinaryNode currentNode) {
BinaryNode newRoot = currentNode.getRight();
currentNode.setRight(currentNode.getRight().getLeft());
newRoot.setLeft(currentNode);
currentNode.setHeight(calculateHeight(currentNode));
newRoot.setHeight(calculateHeight(newRoot));
return newRoot;
}// end of method
// Helper Method
private BinaryNode rightRotate(BinaryNode currentNode) {
BinaryNode newRoot = currentNode.getLeft();
currentNode.setLeft(currentNode.getLeft().getRight());
newRoot.setRight(currentNode);
currentNode.setHeight(calculateHeight(currentNode));
newRoot.setHeight(calculateHeight(newRoot));
return newRoot;
}// end of method
// Helper Method
private int checkBalance(BinaryNode rootLeft, BinaryNode rootRight) {
if((rootLeft == null) && (rootRight == null)) { //if current node is a leaf node then no need to check balance of its children
return 0;
}else if (rootLeft == null) {
return -1 * (rootRight.getHeight() + 1); // if left node node is not there then simply return right node's
// height + 1
// we need to make it -1 because blank height is considered
// having height as '-1'
} else if (rootRight == null) {
return rootLeft.getHeight() + 1;
} else {
return rootLeft.getHeight() - rootRight.getHeight(); // +1 is not required, as both right and left child
// exits and 1 gets nullified
}
}// end of method
// Calculate height of Node
private int calculateHeight(BinaryNode currentNode) {
if (currentNode == null) {
return 0;
}
return 1 + Math.max((currentNode.getLeft() != null ? currentNode.getLeft().getHeight() : -1),
(currentNode.getRight() != null ? currentNode.getRight().getHeight() : -1));
}// end of method
// creates a new blank new node
public BinaryNode createNewNode(int value) {
BinaryNode node = new BinaryNode();
node.setValue(value);
node.setHeight(0);// Since this is a leaf node, its height is 0
return node;
}// end of method
// Level order traversal of BST
void levelOrderTraversal() {
Queue<BinaryNode> queue = new LinkedList<BinaryNode>();
queue.add(root);
System.out.println("Printing Level order traversal of AVL Tree...");
if (root == null) {
System.out.println("Tree does not exists !");
return;
}
while (!queue.isEmpty()) {
BinaryNode presentNode = queue.remove();
System.out.print(presentNode.getValue() + " ");
if (presentNode.getLeft() != null)
queue.add(presentNode.getLeft());
if (presentNode.getRight() != null)
queue.add(presentNode.getRight());
}
}// end of method
// Deleting a node from BST
public void deleteNodeOfBST(int value) {
System.out.println("Deleting " + value + " from AVL Tree ...");
root = deleteNodeOfBST(root, value);
}
// Helper Method for delete
public BinaryNode deleteNodeOfBST(BinaryNode currentNode, int value) {
// THIS ELSE_IF BLOCK IS BST CONDITION
if (currentNode == null)
return null;
if (value < currentNode.getValue()) {
currentNode.setLeft(deleteNodeOfBST(currentNode.getLeft(), value));
} else if (value > currentNode.getValue()) {
currentNode.setRight(deleteNodeOfBST(currentNode.getRight(), value));
} else { // If currentNode is the node to be deleted
//System.out.println("currentNode is the node to be deleted");
if (currentNode.getLeft() != null && currentNode.getRight() != null) { // if nodeToBeDeleted have both children
BinaryNode temp = currentNode;
BinaryNode minNodeForRight = minimumElement(temp.getRight());// Finding minimum element from right subtree
currentNode.setValue(minNodeForRight.getValue()); // Replacing current node with minimum node from right subtree
deleteNodeOfBST(currentNode.getRight(), minNodeForRight.getValue());// Deleting minimum node from right now
} else if (currentNode.getLeft() != null) {// if nodeToBeDeleted has only left child
currentNode = currentNode.getLeft();
} else if (currentNode.getRight() != null) {// if nodeToBeDeleted has only right child
currentNode = currentNode.getRight();
} else { // if nodeToBeDeleted do not have child (Leaf node)
//System.out.println("This node is leaf node");
currentNode = null;
}
return currentNode;// if it is a leaf node,then no need to do balancing for this node, do only for its ancestors
}
// THIS IS WHERE WE WILL DO AVL SPECIFIC WORK
int balance = checkBalance(currentNode.getLeft(), currentNode.getRight());
if (balance > 1) {
if (checkBalance(currentNode.getLeft().getLeft(), currentNode.getLeft().getRight()) > 0) {
currentNode = rightRotate(currentNode);// LL Condition
} else {
currentNode.setLeft(leftRotate(currentNode.getLeft())); // LR Condition
currentNode = rightRotate(currentNode);
}
} else if (balance < -1) {
if (checkBalance(currentNode.getRight().getRight(), currentNode.getRight().getLeft()) > 0) {
currentNode = leftRotate(currentNode);// RR Condition
} else {
currentNode.setRight(rightRotate(currentNode.getRight()));// RL Condition
currentNode = leftRotate(currentNode);
}
}
if (currentNode.getLeft() != null) {
currentNode.getLeft().setHeight(calculateHeight(currentNode.getLeft()));
}
if (currentNode.getRight() != null) {
currentNode.getRight().setHeight(calculateHeight(currentNode.getRight()));
}
currentNode.setHeight(calculateHeight(currentNode));
return currentNode;
}// end of method
// Get minimum element in binary search tree
public static BinaryNode minimumElement(BinaryNode root) {
if (root.getLeft() == null)
return root;
else {
return minimumElement(root.getLeft());
}
}// end of method
void printTreeGraphically() {
Queue<BinaryNode> queue = new LinkedList<BinaryNode>();
Queue<Integer> level = new LinkedList<Integer>();
int CurrentLevel = 1;
boolean previousLevelWasAllNull = false;
queue.add(root);
level.add(1);
System.out.println("\nPrinting Level order traversal of Tree...");
if(root == null) {
System.out.println("Tree does not exists !");
return;
}
while (!queue.isEmpty()) {
if(CurrentLevel == level.peek()) { //if we are in the same level
if(queue.peek()==null) {
queue.add(null);level.add(CurrentLevel+1);
}else {
queue.add(queue.peek().getLeft());level.add(CurrentLevel+1);
queue.add(queue.peek().getRight());level.add(CurrentLevel+1);
previousLevelWasAllNull = false;
}
System.out.print(queue.remove() + " ");level.remove();
}else { //level has changed
System.out.println("\n");
CurrentLevel++;
if(previousLevelWasAllNull == true) {
break;
}
previousLevelWasAllNull = true;
}
}//end of loop
}//end of method
}// end of class
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