Skip to content

Create AVLTree.java #29

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
dynamitechetan merged 1 commit into from
Apr 24, 2017
Merged

Create AVLTree.java #29

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
212 changes: 212 additions & 0 deletions data_structures/AVLTree.java
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,212 @@
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();
}
}