Ds 1

Introduction to Data Structures

Objectives
In this lesson, you will learn to:
Classify and list the types of data structures
List the types of arrays
List the types of linked lists
Implement nodes insertion on single linked list

©NIIT Introduction to Data Structures/Lesson 1/Slide 1 of 34


Data Structures
Data Structure is :
A collection of data items or objects
Relationships among data items or objects
Collection of functions or operations that can be
applied to that data



Types and Classification of Data Structures
Some of the commonly used data structures are:
Strings
Arrays
Linked Lists
Stacks
Queues
Binary trees
Graphs



Types and Classifications of Data Structures
(Contd..)
Data structures can be classified into:
Static data structures (one-dimensional array, two-
dimensional array, and multi-dimensional array)
Dynamic data structures (linked lists, binary trees,
and graphs)
Elastic data structures (stack, queue)
Data structures can also be classified based on the
linkages between the different structures:
Linear Structures (arrays and linked lists)
Hierarchical Structures (binary trees)



Types and Classification of Data Structures
(Contd..)
Network Structures (graphs)



Just a Minute…
2. An array is an example of dynamic data structure. (T/
F)
3. Queues works on a concept of FIFO. (T/F)
4. ______________________ are called terminal
nodes.



Types of Arrays
Arrays are the simplest type of data structures
Arrays are of two types:
One-dimensional arrays
Multi-dimensional arrays



One-dimensional Arrays
Example: Let NOFDAYS be an array of 12 element
representing total number of days in a month.
int NOFDAYS[12];
Then,
NOFDAYS[0] = 31 NOFDAYS[1] = 28
NOFDAYS[2] = 31 and so on...
The array will be represented as shown in the
following figure:
31 28 31 30 31 30

NOFDAYS[0] NOFDAYS[1] NOFDAYS[2]…



Multi-dimensional Arrays
Programming languages like PASCAL, COBOL, C,
and C++ allow declaration of multidimensional arrays.
These can be stored in the memory in the following
two ways:
Row-major order: The elements are listed so that
the last element varies first (more rapidly). Then,
the second last element varies next (less rapidly)
and so on.
Column-major order : The elements are listed so
that the first element varies more rapidly then, the
second element varies next and so on.



Array Referencing
Elements of an array are stored in contiguous
locations
To reference an element in the array we need to
know only the address of the starting element
The first element’s address can be denoted as the
base address of the array
The first element number is known as Lower Bound
The last element number is known as Upper Bound



Array Referencing (Contd..)
From the base address, the computer will calculate
the address of any element with the formula:
BA+LEN*(ENUM-
FNUM)=Address of the required element
Where,
BA is the Base Address
LEN is the length per element
ENUM is the element Number
FNUM is the first element number



Multi-dimensional Arrays (Contd..)
(1, 1) (1, 1)

(2, 1) (1, 2)
Column 1
(3, 1) (1, 3) Row 1

(1, 2) (1, 4)

(2, 2) Column 2 (2, 1)

(3, 2) (2, 2)

(1, 3) (2, 3) Row 2

(2, 3) (2, 4)
Column 3
(3, 3) (3, 1)

(1, 4) (3, 2)

(2, 4) (3, 3) Row 3
Column 4
(3, 4) (3, 4)

Column‑major order Row‑major order



Just a Minute…
2. Find the address of numbers [13] and numbers [40] of
the array numbers [40] assuming a Base address of
250 and length of each element as 4.
3. Matrix is an example of _________ dimensional
array.
4. How many types of arrays are available?



Array Complexities
Inserting and deleting from array involves
complexities.
If an element is deleted from the middle of an
array, then that element remains empty unless all
the names in the succeeding elements are moved
back by one element position to occupy the empty
element.
If an element is inserted in the middle of an array,
all names have to be moved forward by one
element position.



Linked Lists
A linked list is a chain of objects in which each object
consists of the data and a pointer that stores the
address (link) of the next logical object in the list.
The main advantages of linked lists are:
Memory is allocated whenever required.
Inserting to and deleting from linked lists can be
handled efficiently without having to restructure the
list.



Types of Linked Lists
Linked lists can be of different types:
Single linked list
Circular linked list
Double linked list



Single Linked List
Is a chain of structures in which each structure
consists of data and a pointer to the address of next
subsequent node
START

Data LINK Data LINK Data LINK Data LINK

NULL



Circular Linked List
Has the START pointer pointing to the first node and
the last pointer also pointing to the first node

START

Data LINK Data LINK Data LINK Data LINK



Double Linked List
Has 3 parts: the INFO, NEXT pointer, and PREV
pointer
Is also called a two-way list
LAST
START

NULL PREV Data NEXT PREV Data NEXT

NULL

PREV Data NEXT



Operations on Lists
Are:
Insertion
Traversal
Deletion
Modification
Sorting



Some Common Applications of Lists
Are:
Word processing applications
Index maintenance in a file-based database package
Maintenance of linked lists for data files that have
read-write overhead



Complexities in Lists
Are:
The START pointer, pointing to the first node, cannot
be moved as it depicts the starting point of the list.



Single Linked List
The three basic classes that are required to make a
complete linked list are as follows:
A class to represent the DATA or INFO part of the
node.
The Node class, which contains an object of the
built-in data class called INFO and a pointer to a
Node object called NEXT.
The List class that will contain the start pointer to
a Node object.



Insertion Of Nodes In A Linked List
Insertion involves adding a new node to an existing
linked list or creating a new linked list if one does not
already exist.
Insertion can be performed:
At the beginning of the list
In the middle of the list
At the end of the list



Inserting a Node at the Beginning of a
Linked List

Existing Links on the list
Links after inserting the new node

START

INFO NEXT INFO NEXT INFO NEXT

NULL

INFO NEXT



Inserting a Node at the Beginning of a Linked
List (Contd..)
Requires to:
Check whether or not the list exists
Check whether the user supplied string is lesser than
the INFO in the first node



Inserting a Node in the Middle or at the End of a
Linked List

prev
START curr

Ann NEXT Tom NEXT NEXT

NULL

Existing Links on the list
NEXT
Links after inserting the new node



Inserting a Node in the Middle or at the End of a
Linked List (Contd..)
Requires to:
Allocate the memory for the new node.
Position the pointer prev on the node after which the
new node is to be inserted and the pointer curr to be
positioned on the node before which the new node is
to be inserted.
Complete the link by making the NEXT of the previous
node point to the new node.



Problem Statement 1.D.1
Create an application that accepts the names of an
unknown number of customers and displays them in
alphabetical order.



Summary
In this lesson, you learned that:
Data structures are a collection of data values, the
relationships among them, and the functions or
operations that can be applied to the data.
Some of the commonly used data structures are:
Strings
Arrays
Linked lists
Stacks
Queues



Summary (Contd..)
Binary trees
Graphs
Data structures can be categorized as:
Static data structures (multi-dimensional arrays)
Dynamic data structures (linked lists, binary
trees graphs)
Elastic data structures (stack, queue)
The array is the simplest type of data structure. The
elements of an array are stored in contiguous
locations.



Summary (Contd..)
Arrays are of two types—One-dimensional array (also
called linear array) and multi-dimensional arrays.
Arrays will be stored in memory by the programming
language in one of the two ways available:
Column-major order
Row-major order
Linked lists can be of different types:
Single linked list
Circular linked list
Double linked list


Summary (Contd..)
The different operations that can be performed on a linked
list are:
Insertion
Traversal
Modification
Deletion
The three classes, which make a complete linked list are as
follows:
A class to represent the data or INFO part of the node
The Node class, which will contain an object of the
built-in data class called INFO and a pointer to a Node
object called NEXT


Summary (Contd.)
The List class that will contain the starting
pointer to a Node object
The insertion of a node can be performed at three
different levels:
At the beginning of the list
In the middle of the list
At the end of the list


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