static AVLNode rebalancing(AVLNode root) {
root.ht = Math.max(height(root.left), height(root.right)) + 1;
int bf = height(root.left) - height(root.right);
if (bf > 1) {
bf = height(root.left.left) - height(root.left.right);
if (bf < 0) {
root.left = rotate(root.left, true);
}
root = rotate(root, false);
} else if (bf < -1) {
bf = height(root.right.left) - height(root.right.right);
if (bf > 0) {
root.right = rotate(root.right, false);
}
root = rotate(root, true);
}
return root;
}
static AVLNode rotate(AVLNode root, boolean isLeft) {
if (isLeft) {
AVLNode right = root.right;
root.right = right.left;
right.left = root;
root.ht = Math.max(height(root.left), height(root.right)) + 1;
root = right;
root.ht = Math.max(height(root.left), height(root.right)) + 1;
} else {
AVLNode left = root.left;
root.left = left.right;
left.right = root;
root.ht = Math.max(height(root.left), height(root.right)) + 1;
root = left;
root.ht = Math.max(height(root.left), height(root.right)) + 1;
}
return root;
}
// https://www.hackerrank.com/challenges/self-balancing-tree
public AVLNode insert(AVLNode root, int val) {
if (root == null) {
AVLNode node = new AVLNode();
node.val = val;
node.ht = 0;
return node;
}
if (root.val > val) {
root.left = insert(root.left, val);
} else {
root.right = insert(root.right, val);
}
return rebalancing(root);
}