Data structure lecture 1

Lecture - 1
on
Data Structures

Data Type and Data Structure

Data type
•Set of possible values for variables
•Operations on those values
Ex : int, float, char ……….

Data Structure
A data structure is an arrangement of data in a computer's memory
or even disk storage.
The logical and mathematical model of a particular organization of
data is called a data structure.
A data structure is a particular way of storing and organizing data
in a computer so that it can be used efficiently.

An example of several common data structures:
• arrays,
•linked lists,
•stacks,
•queues,
• trees,
•and Graph

Array
Linear array (One dimensional array) : A list of finite number n of similar data
elements referenced respectively by a set of n consecutive numbers, usually 1,
2, 3,…..n. That is a specific element is accessed by an index.
Let, Array name is A then the elements of A is : a1,a2….. an
Or by the bracket notation A[1], A[2], A[3],…………., A[n]
The number k in A[k] is called a subscript and A[k] is called a subscripted
variable.

element

Example
A linear array STUDENT consisting of the name of six students

STUDENT
1 Dalia Rahaman
2 Sumona
3 Mubtasim Fuad
4
Anamul Haque
5
Ibtisam Rahaman
6
Jarin

Here, STUDENT[4] denote Anamul Haque

Array (con…)
Linear arrays are called one dimensional arrays because each
element in such an array is referenced by one subscript.
(Two dimensional array) : Two dimensional array is a collection of
similar data elements where each element is referenced by two
subscripts.
Such arrays are called matrices in mathematics and tables in
business applications.
Multidimensional arrays are defined analogously
MATRICES
1 2 3 4
1 1 2 3 4
Here, MATRICES[3,3]=11
2 5 6 7 8
3 9 10 11 12
4 13 14 15 16

Array Data Structure
It can hold multiple values of a single type.
Elements are referenced by the array name and an ordinal index.
Each element is a value
Indexing begins at zero.
The array forms a contiguous list in memory.
The name of the array holds the address of the first array element.
We specify the array size at compile time, often with a named constant.

Linked lists
•A linked list, or one way list, is a linear collection of data
elements, called nodes, where the linear order is given by means
of pointers.

•Dynamically allocate space for each element as needed.

Node

Data Next

In linked list
Each node of the list contains the data item
a pointer to the next node

Collection structure has a pointer to the list Start
Initially NULL
Start

Prepared by, Jesmin Akhter,
Lecturer, IIT,JU

Linked lists

Start

node
node
Data Next Data

Linked list with 2 nodes

Prepared by, Jesmin Akhter,
Lecturer, IIT,JU

Linked lists
INFO LINK

START 1 START=3, INFO[3]=M

3 2 A 5 LINK[3]=2, INFO[2]=A

3 M 2 LINK[2]=5, INFO[5]=N
LINK[5]=4, INFO[4]=G
4 G 7
LINK[4]=7, INFO[7]=O
5 N 4
LINK[7]=0, NULL value, So the list has ended
6
7 O 0

8

Stacks
• Stacks are a special form of collection
with LIFO semantics
• Two methods
- add item to the top of the stack
- remove an item from the top of the stack
• Like a plate stacker

Queues

• Like a stack, a queue is also a list. However,
with a queue, insertion is done at one end, while
deletion is performed at the other end
• The insertion end is called rear
– The deletion end is called front

Remove Insert
front rear

Data structure operations
The data appearing in our data structure is processed by means of certain
operations. In fact, the particular data structure that one chooses for a given
situation depends largely on the frequency with which specific operations are
performed. The following four operations play a major role:

Traversing
Accessing each record exactly once so that certain items in the record may
be processed. (This accessing or processing is sometimes called 'visiting"
the records.)

Searching
Finding the location of the record with a given key value, or finding the
locations of all records, which satisfy one or more conditions.

Inserting
Adding new records to the structure.

Deleting
Removing a record from the structure.

Data structure operations (Continued)

The following two operations, which are used in special situations, will also be
considered:
Sorting:
Arranging the records in some logical order
Merging:
Combining the records in two different sorted files into a single sorted files

Algorithms
An essential aspect to data structures is algorithms. Data structures
are implemented using algorithms.
An Algorithm is a finite step – by – step list of well defined instructions
for solving a particular problem. It is used to manipulate the data
contained in the data structures as in searching and sorting. It states
explicitly how the data will be manipulated.

Perform data structure operations

Complexity

The complexity of an algorithm is a function describing the efficiency of the
algorithm in terms of the amount of data the algorithm must process. There
are two main complexity measures of the efficiency of an algorithm:

Time complexity is a function describing the amount of time an algorithm
takes in terms of the amount of input to the algorithm.

Space complexity is a function describing the amount of memory (space) an
algorithm takes in terms of the amount of input to the algorithm.

Discussion
•Once data is organized into forms such as trees, stacks and queues,
standard algorithms can be used to process them.

•Properly organized data lead to easy-to understand user interfaces

Data structure lecture 1

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Data structure lecture 1