Data Structures

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Arrays

• Homogenous, fixed-length data structure
• Size is determined on initialization
• Since Array is a fixed-length data structure, you need to copy them to add data.
  • Although you’re better off using a List at this point

static T[] AddToArray<T>(T[] array, T item)
{
    var newArr = new T[array.Length + 1];
    for (var i = 0; i < array.Length; i++) newArr[i] = array[i];
 
    newArr[^1] = item;
    return newArr;
}

Multi-Dimensional Arrays

• Arrays that have more than one dimension, such as a grid
• All rows must have the same length

var map = new int[3, 3, 3]; // 3x3x3 — 3d array

Jagged Arrays

• Arrays of arrays where the rows can be different lengths
• More memory efficient in certain scenarios over multi-dimensional arrays

var jaggedArr = new int[3][][]; // 3 rows

Stack

• LIFO → last in, first out
  • The most recently added item is the one that gets removed when you remove an item
• Stack<T>.Push → adds item to the top of the stack
• Stack<T>.Pop → removes items from the top of the stack

var cardStack = new Stack<Card>();  
cardStack.Push(new Card("Queen", "Hearts"));  
cardStack.Push(new Card("Ace", "Diamonds"));  
cardStack.Push(new Card("Six", "Spades"));  
cardStack.Pop(); // Six of Spades

Queue

• FIFO → first in, first out
  • Items are removed sequentially, in the order that they arrived
• Queue<T>.Enqueue → adds item to the front of the queue
• Queue<T>.Dequeue → removes items from the back of the queue

var cardQueue = new Queue<Card>();  
cardQueue.Enqueue(new Card("King", "Clubs"));  
cardQueue.Enqueue(new Card("Ten", "Hearts"));  
cardQueue.Enqueue(new Card("Two", "Diamonds"));  
cardQueue.Dequeue(); // King of Clubs

Dictionary

• Unordered, key/value pairs
• Dictionary<T>.Remove → removes an item from the dictionary
• Dictionary<T>[Item] → access the item with key Item in the dictionary

var areas = new Dictionary<string, string>();  
areas.Add("Square", "s^2");  
areas.Add("Circle", "πr^2");  
areas.Add("Triangle", "1/2bh");  
Console.WriteLine(areas["Circle"]); // πr^2

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