Arrays and Lists in C#, Java, Python and JavaScript

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Processing Elements in C#, Java, JS and Python
Arrays and Lists in Programming
Svetlin Nakov, PhD
Co-Founder, Innovation and
Inspiration Manager at SoftUni
https://nakov.com

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Have a Question?
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 The 4 groups of software development skills
 Coding, algorithms, development concepts, technologies
 Arrays and lists: processing groups of elements in programming
 Arrays and lists in C#
 Arrays and lists in Java
 Arrays and lists in JavaScript
 Arrays and lists in Python
 How to become a software developer?
Agenda

 Coding skills – 20%
 Algorithmic thinking – 30%
 Fundamental concepts of the
software developer profession – 25%
 Programming languages &
software technologies – 25%
Skills of Software Developers
4

 In programming, an array is a sequence of elements
 Values are typically of the same type (e.g. numbers)
 Elements are numbered: 0 … length-1
 In C# and Java arrays have
fixed size: cannot be resized
What are Arrays?
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Array of 5
elements
(length = 5)
Element index
Element of an array
… … … … …
0 1 2 3 4

 The days of week can be stored in array of strings:
Days of Week – Example
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string[] days = {
"Monday",
"Tuesday",
"Wednesday",
"Thursday",
"Friday",
"Saturday",
"Sunday"
};
Element Value
days[0] Monday
days[1] Tuesday
days[2] Wednesday
days[3] Thursday
days[4] Friday
days[5] Saturday
days[6] Sunday

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 In programming, a list is a resizable sequence of elements
 Some programming languages (like JS and Python) almost do
not distinguish between arrays and lists
 Other linear structures:
 Linked lists: each element holds a value + link to the next
 Stack (last in last out – LIFO)
 Queue (first in, first out – FIFO)
Lists: Indexed, Mutable Sequences of Elements

 List of numbers, representing a sequence of income amounts:
 Adding a new income:
List of Numbers– Example
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var incomes = [
150, 200, 70.50, 120
];
Element Value
incomes[0] 150
incomes[1] 200
incomes[2] 70.50
incomes[3] 120
incomes.push(300); incomes[4] 300

Arrays and Lists in C#
https://gist.github.com/nakov/8ebbd98c22915e5b261d0bb1a8f11608

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Lists in C#
var incomes = new List<double> {
150, 200, 70.50, 120
};
// Print the list using a foreach-loop
Console.WriteLine("Incomes:");
foreach (var amount in incomes)
Console.WriteLine(amount);
// Add a new element
incomes.Add(300);

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Lists in C# (2)
// Print the list using String.Join()
Console.WriteLine("Incomes: {0}n",
String.Join(", ", incomes));
// Calculate count, sum, average, first, second, last
Console.WriteLine("Count = {0}", incomes.Count);
Console.WriteLine("First = {0}", incomes.First());
Console.WriteLine("Second = {0}", incomes.Skip(1).First());
Console.WriteLine("Last = {0}", incomes.Last());
Console.WriteLine("Sum = {0}", incomes.Sum());
Console.WriteLine("Avg = {0}", incomes.Average());

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Lists in C# (3)
// Remove the elements at positions 1 … 3
incomes.RemoveRange(1, 3);
// Print the list using a for-loop
Console.WriteLine("Incomes:");
for (var i = 0; i < incomes.Count; i++)
Console.WriteLine(incomes[i]);
150 200 70.5 120 300
0 1 2 3 4
// Modify an existing element: 20% up
incomes[0] = incomes[0] * 1.20; 150 300
0 1
180 300
0 1

Arrays and Lists in Java

Arrays and Lists
in JavaScript

Arrays and Lists
in Python

How to Become a
Software Engineer?

 First find out if programming is for you!
 Sign up for the SoftUni free coding course
for beginners: https://softuni.bg/apply
 Or follow a tutorial / book / video course on the Internet
 Does programming excite you?
 Do you really like it and enjoy it?
 Are you good at coding problems?
 Do you want to write code all the time?
How do I Become a Software Engineer?
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 Coding skills – 20%
 Algorithmic thinking – 30%
 Fundamental concepts of the
software developer profession – 25%
 Programming languages &
software technologies – 25%
Learn the 4 of Fundamental Skills
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 To become a software engineer, you need to study
hard and consistently for 3000+ hours!
 2 years @ 4 hours daily (average)
 Or 1 year @ 8-10 hours daily
 Developing practical projects
 Write 100K+ lines of code (LOC)
 100K LOC == 300 days * 350 LOC
Study Hard, Very Hard!
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Learning Path: From Zero to First Job
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https://softuni.bg/curriculum

Sign Up for SoftUni!
https://softuni.bg/apply
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Arrays and Lists in C#, Java, Python and JavaScript

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