**AVL Tree-**

- AVL trees are special kind of binary search trees.
- In AVL trees, height of left subtree and right subtree of every node differs by at most one.
- AVL trees are also called as
**self-balancing binary search trees**.

**Example-**

Following tree is an example of AVL tree-

This tree is an AVL tree because-

- It is a binary search tree.
- The difference between height of left subtree and right subtree of every node is at most one.

Following tree is not an example of AVL Tree-

**AVL Tree Operations-**

Like BST Operation commonly performed operations on AVL tree are-

- Search Operation
- Insertion Operation
- Deletion Operation

**Case-01:**

- After the operation, the balance factor of each node is either 0 or 1 or -1.
- In this case, the AVL tree is considered to be balanced.
- The operation is concluded.

**Case-02:**

- After the operation, the balance factor of at least one node is not 0 or 1 or -1.
- In this case, the AVL tree is considered to be imbalanced.
- Rotations are then performed to balance the tree.

**AVL Tree Rotations-**

**Kinds of Rotations-**

There are 4 kinds of rotations possible in AVL Trees-

- Left Rotation (LL Rotation)
- Right Rotation (RR Rotation)
- Left-Right Rotation (LR Rotation)
- Right-Left Rotation (RL Rotation)

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