20 AVL Tree Interview Questions and Answers

An AVL tree is a data structure that is used to store data in a way that is both efficient and easy to search. This makes it a popular choice for many developers who need to store and retrieve data quickly. When interviewing for a position that involves working with AVL trees, it is important to be able to answer questions about this data structure. In this article, we will review some common AVL tree interview questions and how you should answer them.

AVL Tree Interview Questions and Answers

Here are 20 commonly asked AVL Tree interview questions and answers to prepare you for your interview:

1. What is an AVL tree?

An AVL tree is a type of self-balancing binary search tree. In an AVL tree, the heights of the two child subtrees of any node differ by at most one; if at any time they differ by more than one, rebalancing is done to restore this property. Lookup, insertion, and deletion all take O(log n) time in both the average and worst cases, where n is the number of nodes in the tree prior to the operation. Insertions and deletions may require the tree to be rebalanced by one or more tree rotations.

2. Can you explain the basic structure of an AVL tree?

An AVL tree is a type of self-balancing binary search tree. In an AVL tree, the heights of the two child subtrees of any node differ by at most one; if at any time they differ by more than one, rebalancing is done to restore this property. Lookup, insertion, and deletion all take O(log n) time in both the average and worst cases, where n is the number of nodes in the tree prior to the operation. Insertions and deletions may require the tree to be rebalanced by one or more tree rotations.

3. Why are AVL trees called as balanced binary search trees?

AVL trees are called as balanced binary search trees because they maintain a balance factor at each node which is the difference between the heights of the left and right subtrees. This balance factor is used to ensure that the tree remains balanced and provides efficient search operations.

4. When would you choose to use an AVL tree over another data structure like a hash table or dictionary?

AVL trees are used when you need a data structure that can be quickly searched while still maintaining a relatively low memory footprint. This makes them ideal for use in applications where speed is critical, such as in video games or other real-time applications.

5. Is it possible to insert multiple nodes into an AVL tree at once? If yes, then how?

Yes, it is possible to insert multiple nodes into an AVL tree at once. This can be done by first creating a new node with the desired value, and then inserting it into the tree using the standard insertion method. Once the new node has been inserted, the tree will need to be rebalanced.

6. What happens if we try to do an inorder traversal on an empty AVL tree?

An inorder traversal on an empty AVL tree will simply return an empty list.

7. How does an AVL tree handle duplicate elements?

When an AVL tree encounters a duplicate element, it will simply ignore it and move on.

8. How can you determine whether an AVL tree is height-balanced or not?

One way to determine whether an AVL tree is height-balanced is to simply check the height of the left and right subtrees of every node. If the difference in height is greater than 1, then the tree is not balanced.

9. How many different kinds of rotations can be done on an AVL Tree?

There are four different types of rotations that can be done on an AVL Tree: left-left, left-right, right-left, and right-right.

10. Is it possible to retrieve the smallest element in an AVL tree? If yes, then how?

Yes, it is possible to retrieve the smallest element in an AVL tree. This can be done by traversing the tree until you reach a node that has no left child. The element stored in that node will be the smallest element in the tree.

11. What will be the output when doing a post order traversal on an AVL tree?

The output of a post order traversal on an AVL tree will be the values of the nodes in the tree in reverse order.

12. What’s the difference between AVL and Red Black Trees?

The main difference between AVL and Red Black Trees is that AVL Trees are more balanced than Red Black Trees. This means that AVL Trees can be faster when it comes to searching and inserting data, since the data is more evenly distributed. However, Red Black Trees are more flexible when it comes to how the data is organized, so they may be better suited for certain applications.

13. What is the best way to find out whether a given node has a left child or not?

The best way to find out whether a given node has a left child or not is to check the node’s left child pointer. If it is NULL, then the node does not have a left child.

14. What kind of rotation should be performed to balance a tree that is skewed towards its right side?

A right rotation should be performed to balance a tree that is skewed towards its right side.

15. What is LL Rotation?

LL Rotation is a type of tree rotation that is used to balance an AVL tree. In an LL Rotation, the left child of the root node is rotated to the root position, and the root node is moved to the right child position. This type of rotation is used when the left subtree is taller than the right subtree, and the left child of the root is taller than the right child.

16. What is LR Rotation?

LR Rotation is a type of tree rotation that is used to balance an AVL tree. This type of rotation is performed when the left child of the root node is unbalanced and the right child of the left child is taller than the left child of the left child.

17. What is RL Rotation?

RL Rotation is a type of tree rotation that is used to balance an AVL tree. This rotation is performed when the tree is left-heavy and the left child of the tree’s root node is right-heavy. This rotation is performed by first performing a right rotation on the tree’s root node, and then performing a left rotation on the tree’s new root node.

18. What is RR Rotation?

RR Rotation is a type of tree rotation used to balance an AVL tree. In an RR Rotation, the root node is rotated to the right, and the right child node becomes the new root node. This type of rotation is used when the left child node of the root is heavier than the right child node, and the left child node’s left child is also heavier than its right child.

19. Can you give me some examples of real world applications where AVL trees can be used?

AVL trees are used in a number of applications where data needs to be stored in a sorted fashion, but also needs to be quickly accessible. For example, AVL trees are often used in database indexing, in order to quickly find specific records. They are also used in some routing algorithms, in order to find the shortest path between two nodes.

20. What are some important cases for which AVL tree rebalancing needs to be done?

The most important cases for which AVL tree rebalancing needs to be done are when a new node is inserted into the tree, and when a node is deleted from the tree. In both of these cases, the tree may become unbalanced, and rebalancing is necessary in order to maintain the tree’s balance and keep it functioning properly.