Introduction-to-Data-Structure-and-Algorithm.pptx

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Introduction to Data
Structure and Algorithm
Republic of the Philippines
UNIVERSITY OF EASTERN PHILIPPINES
Department of Information Technology
Catarman, Northern Samar, Philippines
Mar Riel C. Abuke
I.T Instructor

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What are Data Structure?
D a t a s t r u c t u r e i s a s t o r a g e t h a t i s u s e d t o s t o r e a n d o r g a n i z e d a t a . I t i s a w a y o f
a r r a n g i n g d a t a o n a c o m p u t e r s o t h a t i t c a n b e a c c e s s e d a n d u p d a t e d e f f i c i e n t l y.
D e p e n d i n g o n y o u r r e q u i r e m e n t a n d p r o j e c t , i t i s i m p o r t a n t t o c h o o s e t h e r i g h t d a t a
s t r u c t u r e f o r y o u r p r o j e c t . F o r e x a m p l e , i f y o u w a n t t o s t o r e d a t a s e q u e n t i a l l y i n t h e
m e m o r y, t h e n y o u c a n g o f o r t h e A r r a y d a t a s t r u c t u r e .
N o t e : D a t a s t r u c t u r e a n d d a t a t y p e s a r e s l i g h t l y d i f f e r e n t . D a t a s t r u c t u r e i s t h e
c o l l e c t i o n o f d a t a t y p e s a r r a n g e d i n a s p e c i f i c o r d e r.

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Types of Data Structure

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Two Main Types of Data Structure
Primitive Data Structure and Non-Primitive Data
Structure
Primitive Data Structure – These are predefined data,
which are supported by the programming language ,
Primitive data structure is the data structure that allows
you to store only single data type values. Built-in Data
Structure
 String = “this is string”
 Integer = 10
 Float = 34.1

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Two Main Types of Data Structure
Non-Primitive Data Structure - is a data structure that allows
you to store multiple data type values.
 These are data structures that are not defined by the
programming language.
 These are created by the programmer
 User defined data structure
Two Types
 Linear List
 Non-Linear List

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Two Main Types of Non-Primitive Data Structure
Linear List – the elements are arranged in sequence one after the other.
Since elements are arranged in particular order, they are easy to
implement.
However, when the complexity of the program increases, the linear data
structures might not be the best choice because of operational
complexities.
Non-Linear List - Unlike linear data structures, elements in non-linear data
structures are not in any sequence. Instead they are arranged in a
hierarchical manner where one element will be connected to one or more
elements.

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Linear List – The data items are arranged in a linear
sequence either Vertically or Horizontally.
Kinds of Linear List
 Array
 Stack
 Queue
 Linked List

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Popular Linear Data Structures
1. Array Data Structure
In an array, elements in memory are arranged in continuous memory. All the
elements of an array are of the same type. And, the type of elements that can
be stored in the form of arrays is determined by the programming language.
An array with each element represented by an index

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C# Array
1. Array Data Structure
In C#, here is how we can declare an array.
datatype[] arrayName;
Here,
dataType - data type like int, string, char, etc
arrayName - it is an identifier
Let's see an example,
int[] age;
Here, we have created an array named age. It can store elements of int type.

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C# Array
But how many elements can it store?
To define the number of elements that an array can hold, we have to allocate
memory for the array in C#. For example,
Here, new int[5] represents that the array can store 5 elements. We can also
say the size/length of the array is 5.
Note: We can also declare and allocate the memory of an array in a single line. For example,
int[] age = new int[5];

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C# Array
In an array, we use an index number to determine the position of each array
element. We can use the index number to initialize an array in C#. For example,
Note:
 An array index always starts at 0. That is,
the first element of an array is at index 0.
 If the size of an array is 5, the index of the
last element will be at 4 (5 - 1).

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Access Array Elements
We can access the elements in the array
using the index of the array. For example,
Output:

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2. Stack Data Structure
In stack data structure, elements are stored in the LIFO principle. That is, the
last element stored in a stack will be removed first.
It works just like a pile of plates where the last plate kept on the pile will be
removed first.
In a stack, operations can be perform only from one end (top here).

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3. Queue Data Structure
Unlike stack, the queue data structure works in the FIFO principle where first
element stored in the queue will be removed first.
It works just like a queue of people in the ticket counter where first person on
the queue will get the ticket first.
In a queue, addition and removal are performed from separate ends.

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4. Linked List Data Structure
In linked list data structure, data elements are connected through a series of
nodes. And, each node contains the data items and address to the next node.

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Non-Linear List – The data items are not in sequence.
Kinds of Non-Linear List
 Tree
 Graph

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Non Linear Data Structures
1. Graph Data Structure
In graph data structure, each node is called vertex and each vertex is
connected to other vertices through edges.
Popular Graph Based Data Structures:
 Spanning Tree and Minimum Spanning Tree
 Strongly Connected Components
 Adjacency Matrix
 Adjacency List

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2. Trees Data Structure
Similar to a graph, a tree is also a collection of vertices and edges. However, in
tree data structure, there can only be one edge between two vertices.
Popular Tree based Data Structure
 Binary Tree
 Binary Search Tree
 AVL Tree
 B-Tree
 B+ Tree
 Red-Black Tree

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Data Structure Hierarchy

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Linear Vs Non-linear Data Structures
Now that we know about linear and non-linear data structures, let's see the
major differences between them.
Linear Data Structures
 The data items are arranged in
sequential order, one after the other.
 All the items are present on the single
layer.
 It can be traversed on a single run.
That is, if we start from the first
element, we can traverse all the
elements sequentially in a single pass.
 The data items are arranged in non-
sequential order (hierarchical
manner).
 The data items are present at
different layers.
 It requires multiple runs. That is, if
we start from the first element it
might not be possible to traverse all
the elements in a single pass.

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Linear Vs Non-linear Data Structures
Now that we know about linear and non-linear data structures, let's see the
major differences between them.
Linear Data Structures
 The memory utilization is not
efficient.
 The time complexity increase with the
data size.
 Example: Arrays, Stack, Queue
 Different structures utilize memory in
different efficient ways depending on
the need.
 Time complexity remains the same.
 Example: Tree, Graph, Map

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What is an Algorithm?
In computer programming terms, an algorithm is a set of well-
defined instructions to solve a particular problem. It takes a set of
input(s) and produces the desired output. For example
An algorithm to add two numbers:
1. Take two number inputs
2. Add numbers using the + operator
3. Display the result

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Characteristics of an Algorithm?
Input – Zero (0) to more
Output – At least one (1)
Definiteness – Instructions must be clear and
realistic
Finiteness – Must terminate and must have a
stopping point
Effectiveness – Instructions must be efficient and
useful

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Qualities of a Good Algorithm
Input and output should be defined precisely.
Each step in the algorithm should be clear and unambiguous.
Algorithms should be most effective among many different
ways to solve a problem.
An algorithm shouldn't include computer code. Instead, the
algorithm should be written in such a way that it can be used in
different programming languages.

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Algorithm Examples:
Algorithm 1: Add two numbers entered by the user

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Algorithm Examples:
Algorithm 2: Find the largest number among three numbers

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Algorithm Examples:
Algorithm 5: Check whether a number is prime or not

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Algorithm : Systematic logical approach which is a
well-defined, step-by-step procedure that allows a
computer to solve a problem.
Pseudocode : It is a simpler version of a
programming code in plain English which uses short
phrases to write code for a program before it is
implemented in a specific programming language.
Program : It is exact code written for problem following
all the rules of the programming language.
Difference between Algorithm, Pseudocode and Program

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Algorithm:
An algorithm is used to provide a solution to a particular problem
in form of well-defined steps. Whenever you use a computer to
solve a particular problem, the steps which lead to the solution
should be properly communicated to the computer. While
executing an algorithm on a computer, several operations such
as additions and subtractions are combined to perform more
complex mathematical operations. Algorithms can be expressed
using natural language, flowcharts, etc.

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Algorithm:
Let’s take a look at an example for a better understanding. As a
programmer, we are all aware of the Linear Search program. (Linear
Search)
Algorithm of linear search :
Here, we can see how the steps of a linear search program are explained
in a simple, English language.

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Pseudocode:
It is one of the methods which can be used to represent an algorithm for a
program. It does not have a specific syntax like any of the programming
languages and thus cannot be executed on a computer. There are several
formats which are used to write pseudo-codes and most of them take down
the structures from languages such as C, Lisp, FORTRAN, etc.
Many time algorithms are presented using pseudocode since they can be
read and understood by programmers who are familiar with different
programming languages. Pseudocode allows you to include several control
structures such as While, If-then-else, Repeat-until, for and case, which is
present in many high-level languages.
Note: Pseudocode is not an actual programming language.

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Pseudocode:
Pseudocode for Linear Search :
In here, we haven’t used any specific programming language but wrote the steps of a
linear search in a simpler form which can be further modified into a proper program.

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Program:
A program is a set of instructions for the computer
to follow. The machine can’t read a program
directly, because it only understands machine
code. But you can write stuff in a computer
language, and then a compiler or interpreter can
make it understandable to the computer.

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Program:
Program for Linear Search :

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Informally, an algorithm is nothing but a mention of steps to solve a problem. They
are essentially a solution.
For example, an algorithm to solve the problem of factorials might look something
like this:
Here, the algorithm is written in English. If it was written in a programming
language, we would call it to code instead. Here is a code for finding the factorial of
a number in PHP.
Data Structure & Algorithm in PHP Implementation

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Programming is all about data structures and algorithms. Data
structures are used to hold data while algorithms are used to
solve the problem using that data.
Data structures and algorithms (DSA) goes through solutions to
standard problems in detail and gives you an insight into how
efficient it is to use each one of them. It also teaches you the
science of evaluating the efficiency of an algorithm. This enables
you to choose the best of various choices.
Data Structure & Algorithm in PHP Implementation

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Time is precious.
Suppose, Alice and Bob are trying to solve a simple problem of finding the sum of
the first 1011 natural numbers. While Bob was writing the algorithm, Alice
implemented it proving that it is as simple as criticizing Donald Trump.
Code by Bob Code by Alice
Use of Data Structures and Algorithms to Make Your Code
Scalable

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Alice and Bob are feeling euphoric of themselves that they could build something
of their own in almost no time. Let's sneak into their workspace and listen to
their conversation.
Alice: Let's run this code and find out the sum.
Bob: I ran this code a few minutes back but it's still not showing the output. What's
wrong with it?
Oops, something went wrong! A computer is the most deterministic machine.
Going back and trying to run it again won't help. So let's analyze what's
wrong with this simple code.
Two of the most valuable resources for a computer program are time and
memory.
Scalable

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The time taken by the computer to run code is:
The number of instructions depends on the code you used, and the time taken to
execute each code depends on your machine and compiler.
Scalable

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End of Lesson

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