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AVLChecker.java
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AVLChecker.java
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class TreeNode {
int value;
TreeNode left;
TreeNode right;
TreeNode(int value) {
this.value = value;
this.left = null;
this.right = null;
}
}
public class AVLChecker {
// Function to calculate the height of a tree
private static int height(TreeNode node) {
if (node == null)
return 0;
return 1 + Math.max(height(node.left), height(node.right));
}
// Function to check if the tree is AVL
public static boolean isAVL(TreeNode root) {
if (root == null)
return true;
// Check if the height difference of the left and right subtrees is not more than 1
if (Math.abs(height(root.left) - height(root.right)) <= 1) {
// Recursively check if both left and right subtrees are AVL
return isAVL(root.left) && isAVL(root.right);
}
return false;
}
// Function to perform left rotation
private static TreeNode leftRotate(TreeNode root) {
TreeNode newRoot = root.right;
root.right = newRoot.left;
newRoot.left = root;
return newRoot;
}
// Function to perform right rotation
private static TreeNode rightRotate(TreeNode root) {
TreeNode newRoot = root.left;
root.left = newRoot.right;
newRoot.right = root;
return newRoot;
}
// Function to balance the tree if it's not AVL
public static TreeNode balanceTree(TreeNode root) {
if (root == null)
return null;
int balanceFactor = height(root.left) - height(root.right);
// Left heavy
if (balanceFactor > 1) {
// Left-Right case
if (height(root.left.right) > height(root.left.left)) {
root.left = leftRotate(root.left);
}
// Left-Left case
root = rightRotate(root);
}
// Right heavy
else if (balanceFactor < -1) {
// Right-Left case
if (height(root.right.left) > height(root.right.right)) {
root.right = rightRotate(root.right);
}
// Right-Right case
root = leftRotate(root);
}
return root;
}
public static void main(String[] args) {
// Example input 1
TreeNode root1 = new TreeNode(1);
root1.left = new TreeNode(2);
root1.right = new TreeNode(3);
if (isAVL(root1)) {
System.out.println("Output 1: 1 (The binary tree is an AVL tree)");
} else {
System.out.println("Output 1: 0 (The binary tree is not an AVL tree)");
System.out.println("Balancing the tree...");
root1 = balanceTree(root1);
System.out.println("Balanced tree is now AVL: " + isAVL(root1));
}
// Example input 2
TreeNode root2 = new TreeNode(1);
root2.left = new TreeNode(2);
root2.left.left = new TreeNode(3);
if (isAVL(root2)) {
System.out.println("Output 2: 1 (The binary tree is an AVL tree)");
} else {
System.out.println("Output 2: 0 (The binary tree is not an AVL tree)");
System.out.println("Balancing the tree...");
root2 = balanceTree(root2);
System.out.println("Balanced tree is now AVL: " + isAVL(root2));
}
}
}