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Balancing an AVL Tree using C++

An AVL tree is a type of self-balancing binary search tree that was invented by Adelson-Velsky and Landis in 1962. This data structure is wi...

An AVL tree is a type of self-balancing binary search tree that was invented by Adelson-Velsky and Landis in 1962. This data structure is widely used in computer science and is known for its efficient insertion, deletion, and search operations. In this article, we will explore the concept of balancing an AVL tree using the popular programming language, C++.

Before we dive into the details of balancing an AVL tree, let's first understand what exactly an AVL tree is. As mentioned earlier, it is a type of binary search tree where every node follows the AVL tree property, which states that the difference between the heights of the left and right subtrees of any node should not exceed one. This property ensures that the tree remains balanced, which in turn results in optimal performance.

Now, let's move on to the main topic of this article - balancing an AVL tree. The process of balancing an AVL tree involves performing rotations on the tree whenever an insertion or deletion operation causes an imbalance. These rotations help in maintaining the AVL tree property and thus, keeping the tree balanced.

To better understand this process, let's consider an example. Suppose we have an AVL tree with the following structure:


/ \

5 15

/ \

3 7

Now, let's say we want to insert the value 12 into this tree. After the insertion, the tree will look like this:


/ \

5 15

/ \ /

3 7 12

As you can see, this insertion has caused an imbalance at the root node, where the left subtree has a height of 2 and the right subtree has a height of 1. According to the AVL tree property, this difference should not exceed one. So, to balance the tree, we perform a left rotation at the root node.

After the rotation, the tree will look like this:


/ \

7 15

/ \

5 12



As you can see, the tree is now balanced, and the AVL tree property is satisfied. This is the basic idea behind balancing an AVL tree - performing rotations to maintain the balance.

Now, let's see how we can implement this in C++. The first step is to create a class for the AVL tree. This class will contain functions for insertion, deletion, and balancing the tree. We will also define a structure for the nodes of the tree, which will contain the value, height, and pointers to the left and right subtrees.

Next, we need to write the code for balancing the tree. This will involve checking the balance factor of each node and performing rotations if necessary. The balance factor of a node is calculated by subtracting the height of its left subtree from the height of its right subtree. If the balance factor is greater than one or less than negative one, it means that the tree is imbalanced, and a rotation needs to be performed.

There are four types of rotations that can be performed on an AVL tree - left rotation, right rotation, left-right rotation, and right-left rotation. These rotations are similar to the example we saw earlier, but they can be applied to different nodes depending on the imbalance.

After writing the code for balancing the tree, we can test our implementation by inserting and deleting values from the tree. With proper rotations, the tree should always remain balanced, and the AVL tree property should be satisfied.

In conclusion, balancing an AVL tree is an essential aspect of maintaining this data structure. It ensures optimal performance and prevents the tree from becoming skewed, which can lead to inefficient operations. By understanding the concept of balancing and implementing it in C++, we can utilize the benefits of this powerful data structure in our programs.

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