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AVLTree.java

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public class AVLTree {

private Node root;

private class Node {

private int key;

private int balance;

private int height;

private Node left, right, parent;

Node(int k, Node p) {

key = k;

parent = p;

}

}

public boolean insert(int key) {

if (root == null)

root = new Node(key, null);

else {

Node n = root;

Node parent;

while (true) {

if (n.key == key)

return false;

parent = n;

boolean goLeft = n.key > key;

n = goLeft ? n.left : n.right;

if (n == null) {

if (goLeft) {

parent.left = new Node(key, parent);

} else {

parent.right = new Node(key, parent);

}

rebalance(parent);

break;

}

}

}

return true;

}

private void delete(Node node){

if(node.left == null && node.right == null){

if(node.parent == null) root = null;

else{

Node parent = node.parent;

if(parent.left == node){

parent.left = null;

}else parent.right = null;

rebalance(parent);

}

return;

}

if(node.left!=null){

Node child = node.left;

while (child.right!=null) child = child.right;

node.key = child.key;

delete(child);

}else{

Node child = node.right;

while (child.left!=null) child = child.left;

node.key = child.key;

delete(child);

}

}

public void delete(int delKey) {

if (root == null)

return;

Node node = root;

Node child = root;

while (child != null) {

node = child;

child = delKey >= node.key ? node.right : node.left;

if (delKey == node.key) {

delete(node);

return;

}

}

}

private void rebalance(Node n) {

setBalance(n);

if (n.balance == -2) {

if (height(n.left.left) >= height(n.left.right))

n = rotateRight(n);

else

n = rotateLeftThenRight(n);

} else if (n.balance == 2) {

if (height(n.right.right) >= height(n.right.left))

n = rotateLeft(n);

else

n = rotateRightThenLeft(n);

}

if (n.parent != null) {

rebalance(n.parent);

} else {

root = n;

}

}

private Node rotateLeft(Node a) {

Node b = a.right;

b.parent = a.parent;

a.right = b.left;

if (a.right != null)

a.right.parent = a;

b.left = a;

a.parent = b;

if (b.parent != null) {

if (b.parent.right == a) {

b.parent.right = b;

} else {

b.parent.left = b;

}

}

setBalance(a, b);

return b;

}

private Node rotateRight(Node a) {

Node b = a.left;

b.parent = a.parent;

a.left = b.right;

if (a.left != null)

a.left.parent = a;

b.right = a;

a.parent = b;

if (b.parent != null) {

if (b.parent.right == a) {

b.parent.right = b;

} else {

b.parent.left = b;

}

}

setBalance(a, b);

return b;

}

private Node rotateLeftThenRight(Node n) {

n.left = rotateLeft(n.left);

return rotateRight(n);

}

private Node rotateRightThenLeft(Node n) {

n.right = rotateRight(n.right);

return rotateLeft(n);

}

private int height(Node n) {

if (n == null)

return -1;

return n.height;

}

private void setBalance(Node... nodes) {

for (Node n : nodes) {

reheight(n);

n.balance = height(n.right) - height(n.left);

}

}

public void printBalance() {

printBalance(root);

}

private void printBalance(Node n) {

if (n != null) {

printBalance(n.left);

System.out.printf("%s ", n.balance);

printBalance(n.right);

}

}

private void reheight(Node node){

if(node!=null){

node.height=1 + Math.max(height(node.left), height(node.right));

}

}

public static void main(String[] args) {

AVLTree tree = new AVLTree();

System.out.println("Inserting values 1 to 10");

for (int i = 1; i < 10; i++)

tree.insert(i);

System.out.print("Printing balance: ");

tree.printBalance();

}

}