Lesson 1 - Introduction to Algorithms.pptx

Introduction to Algorithms
Algorithm
Analysis
&
Design March 2020
1
S. Hassan Adelyar, Ph.D
Instructor of Computer Science Faculty
Kabul University
December 2020
Lesson I: Algorithm Analysis & Design

Algorithm
Analysis
&
Design March 2020
2
Course Information
 Course Name: Algorithm Analysis & Design
 Course Code: SE0601
 Credit hours: 4
 Reference: Jeffrey J. McConnell (2001). Analysis of
Algorithms: An Active Learning Approach. Jones and
Bartlett Publishers, Canada.
 Pre-requisites: Programming Fundamentals, Data
Structures and Discreet Mathematics.
 The contents of the course is divided into 16 lessons.
 Each lesson include presentation, video, quiz, &
discussion.
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Algorithm
Analysis
&
Design March 2020
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Learning Outcome
 By the end of this presentation, students will
be able to:
 Understand Algorithms
 Understand the design of Algorithms
 Understand flow chart & Pseudocode
 Understand the properties of Algorithms
 Understand the importance of Algorithms
 Recognize the types of Algorithms
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Algorithm
Analysis
&
Design March 2020
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Algorithm
 Series of Steps for solving a problem
 Set of instructions
 Transfer input to output
 Solve a specific task
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Analysis
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Design March 2020
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Implementing Algorithms
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Analysis
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Design March 2020
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 Example
 Sorting
 Searching
 Find Minimum
 Find Maximum
 Find shortest path between two points
 Etc.
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Analysis
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 Algorithms can be expressed in many ways:
 Flow charts
 Pseudo-code
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Analysis
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Design March 2020
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Flow Chart Example
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Analysis
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Design March 2020
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Pseudo-code
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x = 0
while (x < 25)
print x
end

Algorithm
Analysis
&
Design March 2020
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Properties of Algorithm
 Finiteness
 Definiteness
 Input
 Output
 Effectiveness
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Analysis
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Design March 2020
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Importance of Algorithm
 Algorithm as a Technology
 Processing of a large amount of data.
 Execution time is very important when
processing a large amount of input.
 Algorithms solve the same problem in
different time.
 Differences can be much more than
hardware.
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Analysis
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Design March 2020
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 Efficiency:
 Suppose computers were infinitely fast. Would you
have any reason to study algorithm?
 Good software engineering practice.
 Select the easiest implementation.
 New application demand increase in speed.
 Time is a non-linear function of the input size.
 This can reduce their ability to benefit from the
increase in speed when the input size is large.
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Algorithm
Analysis
&
Design March 2020
13
Examples
 Linear Search & Binary Search
 Insertion Sort, Merge Sort & Quick Sort
 Fibonacci by recursion, iteration, dynamic
approach
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Algorithm
Analysis
&
Design March 2020
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 The execution time of many complex
algorithms can vary due to factors other than
the size of the input.
 For example, sorting items that are already
sorted.
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Analysis
&
Design March 2020
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Factors that Affect Speed
 Problem being solved
 Programming language
 Compiler
 Computer hardware
 Programmer ability
 Algorithm
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Algorithm
Analysis
&
Design March 2020
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Types of algorithms
 Recursive Algorithms
 Backtracking Algorithms
 Divide-and-conquer Algorithms
 Dynamic Programming Algorithms
 Greedy Algorithms
 Brute Force Algorithms
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Algorithm
Analysis
&
Design March 2020
17 Summary
 In this presentation, we studied Algorithms &
Algorithm design techniques.
 The presentation of Algorithm with the flowchart
& pseudocode was explained with examples.
 In addition to Algorithm, the properties of
Algorithms, importance of Algorithms & types
of Algorithms were explained
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Analysis
&
Design March 2020
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Exercises
 Write an algorithm in pseudo-code to count the
number of capital letters in a file of text. How
many comparisons does it do? What is the fewest
number of increments it might do? What is the
largest number?
 There is a set of numbers stored in a file, but we
don’t know how many it contains. Write an
algorithm in pseudo-code to calculate the average
of the numbers stored in this file. What type of
operations does your algorithm do? How many of
each of these operations does your algorithm do?
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Analysis
&
Design March 2020
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 Write an algorithm to ﬁnd the second largest
element in a list of N values. How many
comparisons does your algorithm do in the worst
case?
 1- Write an algorithm and draw a flowchart to
convert the length in feet to centimeter.
 2- Write an algorithm and draw a flowchart that will
read the two sides of a rectangle and calculate its
area.
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Lesson 1 - Introduction to Algorithms.pptx

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