finish lecture 5

5-arrays-and-lists.md

@@ -1,204 +1,208 @@
-# Arrays and Lists
+---
-
+marp: true
-![](imgs/5%20Arrays%20and%20Lists_0.png)
+paginate: true
-
+math: mathjax
+theme: buutti
+title: 5. Arrays and Lists
 ---
 
-# Overview
+# Arrays and Lists
-
-Arrays
-
-Multidimensional Arrays
-
-Lists
-
-Iterating a List
-
-Foreach
 
-# Arrays
+<!-- headingDivider: 5 -->
+<!-- class: invert -->
 
-Arrays are a collection of variables of the same type, which allocate neighboring memory locations
+## Overview
 
-A single value in this collection is called an  __element__
+* Arrays
+* Multidimensional arrays
+* Lists
+* Iterating a list
+* Foreach
 
-Arrays can be  __declared __ with square brackets following the type of the elements:
+## Arrays
 
+* Arrays are a collection of variables of the same type
+* To optimize memory usage, arrays allocate neighbouring memory addresses
+* A single value in this collection is called an *__element__*
+* Arrays can be *__declared__* with square brackets following the type of the elements:
+  ```csharp
   int[] userIds;
+  ```
+* Declaring an array does not yet allocate space from memory
 
-Declaring an array does not yet allocate space from memory
+### Initializing arrays 
-
-# Arrays (continued)
-
-__Initialize __ an array with a length of 3 using the following syntax:
 
+* *__Initialize__* an array with a length of 3 using the following syntax:
+  ```csharp
   int[] userIds = new int[3];
-
+  ```
-__Assign a value__  to an element in an array by specifying the index in square brackets:
+* *__Assign a value__* to an element in an array by specifying the index in square brackets:
-
+  ```csharp
   userIds[0] = 104;
+  ```
+* Indexing starts from 0, so the above line assigns a value of `104` to the ***first*** element of the array
 
-Indexing starts from 0, so the above line assigns a value of 104 to the first element of the array
+---
-
-You can also create an array containing values with one statement:
 
+* You can also create an array and instantly populate it with values with one statement:
+  ```csharp
   string[] names = new string[3] { "Johannes", "Rene", "Ville" };
-
+  ```
-The same works without specifying the length in the brackets:
+* The same works without specifying the length in the brackets:
-
+  ```csharp
   double[] balances = new double[] { 1.3, 200.3, 9332.14 };
+  ```
 
-# Multidimensional Arrays
+## Multidimensional Arrays
-
-C# supports multidimensional arrays:
 
+* C# supports multidimensional arrays
+* Here's an example of a two-dimensional array.
+* You can think of it as an array consisting of arrays
+  ```csharp
   char[,] letters = new char[3, 4]
-
   {
-
     {'a', 'b', 'c', 'd'},
-
     {'e', 'f', 'g', 'h'},
-
     {'i', 'j', 'k', 'l'}
-
   };
   
   Console.WriteLine(letters[1, 3]);       // Outputs "h"
+  ```
 
-# Lists
+## Lists
-
-The .NET Framework Class Library offers another way to hold multiple variables: the  _List _ object
-
-Declaration and initialization:
 
+* The .NET Framework Library [`System.Collections.Generic`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic?view=net-9.0) offers another structure to contain multiple variables: the [List](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.list-1?view=net-9.0) class
+* Importing the library:
+  ```csharp
+  using System.Collections.Generic;
+  ```
+* Declaration and initialization:
+  ```csharp
   List<int> userIds = new List<int>();
-
+  ```
-Value assignment:
+* Value assignment (exactly like arrays):
-
+  ```csharp
   userIds[0] = 22;
+  ```
 
-# Lists (continued)
+### Why lists?
-
-The key benefit of using Lists lies in its built-in functionalities
 
+* The key benefit of using Lists lies in its built-in functionalities
   ![](imgs/5%20Arrays%20and%20Lists_1.png)
+* You can see a list (heh) of available methods in Visual Studio by following the list variable with a dot
 
-You can see a list of available methods in VSC2019 by following a variable with a dot
+## Arrays vs Lists
-
-# Arrays vs Lists
-
-The memory allocation of an array is static/fixed, but list memory is dynamic
-
-This allows the flexible mutation of lists, meaning you can always add or remove and hence change change the length of the list without issues
 
-![](imgs/5%20Arrays%20and%20Lists_2.png)
+* The memory allocation of an array is ***static*** a.k.a. fixed, but list memory is ***dynamic***
+* This allows the flexible mutation of lists, meaning you can always add or remove elements, thus changing the length of the list without issues
+  ```csharp
+  List<int> intList = new List<int>() { 1, 9, 4 };
+  intList.Remove(0); // List is now [9, 4]
 
-# Arrays vs Lists (continued)
+  int[] intArray = new int[] { 1, 9, 4 };
+  intArray.Remove(0);
+  // Can't do that, array is static
+  // and doesn't include such method
+  ```
 
-When to use arrays and when lists?
+### When to use arrays or lists?
 
-Use  __arrays __ if you need  __high performance__
+* Use arrays when you...
+  * ...need high performance
+  * ...can predetermine the number of elements 
+* Use lists when you...
+  * ...need to add/remove elements dynamically
+  * ...need the list operations
 
-Use  __lists __ if you need support for  __list operations__
+## Example: Iterating an array with a for loop
 
-# Iterating an Array With for Loop - Example
+<div class='columns21' markdown='1'>
+<div markdown='1'>
 
+```csharp
 string[] names = new string[]
-
 {
-
   "Harry Potter",
-
   "Luke Skywalker",
-
   "Harley Quinn"
-
 };
 
 for (int i = 0; i < names.Length; ++i)
-
 {
-
   Console.WriteLine(names[i]);
-
 }
+```
 
-![](imgs/5%20Arrays%20and%20Lists_3.png)
+</div>
+<div markdown='1'>
 
-# Iterating a List
+![](imgs/5%20Arrays%20and%20Lists_3.png)
 
-You can iterate the elements of a list with a for loop the same way as an array
+</div>
+</div>
 
-Just use List.Count instead of Array.Length
+## Iterating a List
 
+* You can iterate the elements of a list with a for loop the same way as an array
+* Just use `List.Count` instead of `Array.Length`
+  ```csharp
   List<int> numbers = new List<int>() { 1, 5, 3 };
-
   int sum = 0;
-
   for (int i = 0; i < numbers.Count; ++i)
-
   {
-
     sum += numbers[i];
-
   }
-
   // sum is now 9
+  ```
 
-# foreach Statement
+## `foreach` Statement
 
-There is one more statement to use to iterate arrays and lists: the foreach statement
+* There is one more statement to use to iterate arrays and lists: the `foreach` statement
+* `foreach` is useful when you have to execute code for each element of an array or a list, and don't need the corresponding index:
 
-foreach is useful when you have to execute code for each element of an array or a list:
+<div class='columns21' markdown='1'>
+<div markdown='1'>
 
+```csharp
 string[] names = new string[]
-
 {
-
   "Harry Potter",
-
   "Luke Skywalker",
-
   "Harley Quinn"
-
 };
 
 foreach (string name in names)
-
 {
-
   Console.WriteLine(name);
-
 }
+```
+
+</div>
+<div markdown='1'>
 
 ![](imgs/5%20Arrays%20and%20Lists_4.png)
 
-# foreach Statement (continued)
+</div>
+</div>
 
-However, foreach creates a copy of each element in the object so the element cannot be mutated directly:
+### Note about `foreach`
 
+* However, `foreach` creates a copy of each element in the object so the element cannot be mutated directly:
   ![](imgs/5%20Arrays%20and%20Lists_5.png)
+* Performance-wise, using foreach is also more costly because it uses more memory space
+* If you need to change every element, consider creating a new list instead
 
-Performance-wise, using foreach is also more costly because it uses more memory space
+## Exercise 1: Expanding the Console Application
-
+<!--_class: "exercise invert" -->
----
-
-Instead, create a new list
-
-# Exercise 1: Expanding the Console Application
-
-Continue working on the command line application you created in "The Main Loop" exercise. Add a new command "add" which prompts the user to write a note.
-
-After the user has inputted the note, it is saved to a list, and the program returns back to listening to commands.
-
-Add another command "list" which prints all the saved notes.
 
-Add one more command "remove" which prints all the saved notes with the index of the note, and then prompts the user for a number. After entering the number the corresponding note is deleted from the list.
+1) Continue working on the command line application you created in [Lecture 4, Exercise 1: The Main Loop ](4-loops#exercise-1-the-main-loop). Add a new command `add` which prompts the user to write a note.
+2) After the user has inputted the note, save it to a list, and return back to listening to commands.
+3) Add another command `list` which prints all the saved notes.
+4) Add one more command `remove` which prints all the saved notes with the index of the note, and then prompts the user for a number. After entering the number the note with the corresponding index is deleted from the list.
 
-( __Note__ : you can use int.Parse() -method to parse the user input string to an integer)
+* *__Note__*: you can use the `int.Parse()` method to parse the user input string to an integer
 
-# Assignments
+## Assignments
 
 [Assignments about this topic can be found here](https://gitea.buutti.com/education/academy-assignments/src/branch/master/C%23%20Basics/5.%20Arrays%20&%20Lists)