Computer Science-Data Structures :Abstract DataType (ADT)

Data Structures :Abstract DataType (ADT)
Praseetha E
Assistant Professor
Department of Computer Science&Applications
St. Mary’s College
Thrissur-680020
Kerala

Data Structures,Praseetha E,St.Mary’s College
Abstract Data Type (ADT)
 To process data with a computer, we need to define the data type and
the operation to be performed on the data.
 The definition of the data type and the definition of the operation to
be applied to the data is part of the idea behind an abstract data type
(ADT)
 ADT means to hide how the operation is performed on the data.
 In other words, the user of an ADT needs only to know that a set of
operations are available for the data type, but does not need to know
how they are applied.

Simple ADTs
 Many programming languages already define some simple ADTs as
integral parts of the language.
 For example, the C language defines a simple ADT as an integer. The
type of this ADT is an integer with predefined ranges.
 C also defines several operations that can be applied to this data type
(addition, subtraction, multiplication, division and so on).
 C explicitly defines these operations on integers and what we expect
as the results. A programmer who writes a C program to add two
integers should know about the integer ADT and the operations that
can be applied to it.

Complex ADTs
 Although several simple ADTs, such as integer, real, character,
pointer and so on, have been implemented and are available for use in
most languages, many useful complex ADTs are not.
 As we will see in this session, we need a list ADT, a stack ADT, a
queue ADT and so on. To be efficient, these ADTs should be created
and stored in the library of the computer to be used.

Stack
 A stack is a restricted data structure in which all additions and
deletions are made at one end, the top.
 If we insert a series of data items into a stack and then remove
them, the order of the data is reversed. This reversing attribute is
why stacks are known as last in, first out (LIFO) data structures.
Fig: Three representations of stacks

Operations on stack
There are two basic operations can be applied to a stack:
 Push operation
 Pop operation
The push operation
The following shows the format.
Fig :Push operation

The pop operation
The following shows the format.
Fig :Pop operation
 The pop operation deletes the item at the top of the stack.

Stack: Applications
1.Parsing
2.Recursive Function
3.Expression Evaluation
4.Expression Conversion
1.Infix to Postfix
2.Infix to Prefix
3.Postfix to Infix
4.Prefix to Infix
5.Towers of hanoi

Queue
 A queue is a linear list in which data can only be inserted at one end,
called the rear, and deleted from the other end, called the front.
 These restrictions ensure that the data is processed through the queue
in the order in which it is received. In other words, a queue is a first
in, first out (FIFO) structure.
Fig: Two representation of queues

Operations on queue
There are two basic operations that can be applied to a queue:
 Enqueue operation
 Dequeue operation
The enqueue operation
The following shows the enqueue operation:
Fig: The enqueue operation

The dequeue operation
 The dequeue operation deletes the item at the front of the queue.
The following shows the enqueue operation:
Fig: The dequeue operation

Queue :Applications
Queue is used when things don’t have to be processed immediately, but
have to be processed in First In First Out order.
1. When a resource is shared among multiple consumers. Examples
include CPU scheduling, Disk Scheduling.
2. When data is transferred asynchronously (data not necessarily
received at same rate as sent) between two processes. Examples
include IO Buffers, pipes, file IO, etc.

Linked list
 Linked list is a list in which operations, such as insertion and
deletion, can be done anywhere in the list-at the beginning, in the
middle or at the end. Fig. shows a general linked list.
Fig: Linked list

Operations on Linked list
There are two basic operations that can be applied to a linked list:
 Insert operation
 Delete operation
The insert operation
 Since in a general linked list, insertion can be done in any
position. To determine where the element is to be placed,
searching is needed.
Fig:The insert operation

The delete operation
 Deletion from a linked list also requires that the list be searched to
locate the data to be deleted. After the location of the data is found,
deletion can be done.
Fig: The dequeue operation
The following shows the Eg:

Linked list :Applications
1.Implementation of stacks and queues
2.Implementation of graphs : Adjacency list representation of
graphs is most popular which is uses linked list to store
adjacent vertices.
3.Dynamic memory allocation : We use linked list of free
blocks.
4.Performing arithmetic operations on long integers
5.Manipulation of polynomials by storing constants in the node
of linked list
6.Representing sparse matrices

Tree
 A tree consists of a finite set of elements, called nodes (or
vertices) and a finite set of directed lines, called arcs, that
connect pairs of the nodes.
Fig: Tree representation

 Each node in a tree may have a subtree. The subtree of each
node includes one of its children and all descendents of that
child.
Figure shows all subtrees for the above tree
Fig: Subtrees

Operations on tree:
There are three basic operations that can be applied on a tree:
 Insert operation
 Delete operation
 Traversal operation

Tree traversals
 A tree traversal requires that each node of the tree be processed
once and only once in a predetermined sequence.
There are 3 approaches used in traversing a tree :
Fig: Tree representation

Tree :Applications
1.Heap is a tree data structure which is implemented using arrays
and used to implement priority queues.
2.B-Tree and B+ Tree : They are used to implement indexing in
databases.
3.Syntax Tree: Used in Compilers.
4.Expression evaluation

 An arithmetic expression can be represented in three different
formats: infix, postfix and prefix.
 In an infix notation, the operator comes between the two operands.
 In postfix notation, the operator comes after its two operands.
 In prefix notation it comes before the two operands. These formats
are shown below for addition of two operands A and B.
Expression tree

Fig: Expression tree

Reference :
“Data Structures and Program Design in C” by Kruse Robert L
“Data Structure Using C” by A K Sharma
“Data structures” by Seymour Lipschutz

Computer Science-Data Structures :Abstract DataType (ADT)

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Computer Science-Data Structures :Abstract DataType (ADT)