CS301 Final Term Short Notes

CS301 Data Structures Lecture Wise Questions and Answers For Final Term Exam Preparation By Virtualians Social Network

Lec 23:

Double rotation is simply making a single rotation twice, once left then right or vice versa. While inserting a node in an AVL tree, if we have to balance the tree, then we need to do only one single right, left or one double rotation to balance the tree.

In deletion from an AVL tree, we delete node as we delete it in a BST.

After deleting the node, we traverse up the tree from the deleted node checking the balance of each node at each level up to the root.

Deletion cases in AVL:

Case1a:

The parent of the deleted node had a balance of 0 and the node was deleted in the parent‟s left sub tree.

Action Change the balance of the parent node and stop.

parent‟s right sub tree.

Action change the balance of the parent node and stop.

Case2a: Parent of the deleted node had a balance of 1 and the node was deleted in the parent‟s left sub tree.

Action Change the balance of the parent node. This deletion of node may have caused imbalance in higher nodes so it is advised to continue up to the root of the tree.

Q.when we use " using namespace std" what does it mean? often time i hear the word only namespace, what is meant by namespace alone?

It is not mandatory to use using namespace std; in the beginning of your program, however it is better to use it. It is a combination of some objects, class and functions etc. Q. Why Hoffman tree is not an AVL Tree?

Ans

For a tree to be AVL, there are two conditions:

1. Tree must be Binary Search Tree
2. For every node, height of left and right subtree may differ by at most 1

For Huffman encoding, we also need a Binary tree to get the codes of characters. And we have different method to build that Binary tree. Very Important: Binary tree used in Huffman encoding is not even Binary Search Tree.

Q. Abstract data type (ADT)

Ans

Abstract data type (ADT): A data type whose properties (domain and operations) are specified independently of any particular implementation.

List, for example, is an ADT. The functionality of an ADT can be implemented in many ways. The programs that use these ADTs will not need to know which implementation was used as long as it performs the required functionality.

The List ADT can be implemented through Arrays (elementary data structure that exists as built-in in most programming languages) or linked-structure (list implemented through linked-structure is called Linked-list).

Programming languages provide some built-in data types, also called primitive data types. Like C++ language provides int, float, char etc as built-in data types. Lec : 24:

parent‟s right subtree.

Action Change the balance of the parent tree and in case the imbalance occurs in the higher nodes, continue up the tree.

Case 3a The parent had balance of -1 and the node was deleted in the parent‟s left subtree while right subtree was un-balanced.

Action Perform single rotaion, adjust balance. Balance of the higher nodes will not be affected so that‟s it.

Case 4a Parent had balance of -1 and the node was deleted in the parent‟s left subtree, right subtree was unbalanced.

Action Double rotation to bring the root(B) upwards.

Case 5a the parent had balance of -1 and the node was deleted in the parent‟s left subtree, right subtree was unbalanced.

Acction Single rotation at B. In case of unbalance, continue up the tree.

Expression trees Parse trees and abstract syntax trees , which are significant components of compilers.

The parse trees are used in query processing. The queries are questions to the database to see a particular kind of data. The language used to query is called SQL(Structured Query Language).

Optimizers use the expressions trees and convert them into graphs for efficiency purposes.