DATA

STRUCTURES

WE'VE HIT A

TURNING POINT IN THE COURSE

Singly Linked Lists

Doubly Linked Lists

Directed Graphs

Undirected Unweighted Graphs

Binary Search Trees

Stacks

Queues

Binary Heaps

Hash Tables

WHAT DO THEY DO?

Data structures are collections of values, the relationships among them, and the functions or operations that can be applied to the data

WHY SO MANY???

Different data structures excel at different things.  Some are highly specialized, while others (like arrays) are more generally used.

WHY CARE?

The more time you spend as a developer, the more likely you'll need to use one of these data structures

You've already worked with many of them unknowingly!

And of course...INTERVIEWS

THERE IS NO ONE "BEST"

DATA STRUCTURE

They all excel in different situations...

Otherwise why bother learning them all??

Working with

map/location data?

Use a graph!

Need an ordered list with fast inserts/removals at the beginning and end?

Use a linked list!

Web scraping nested HTML?

Use a tree!

Need to write a scheduler?

Use a binary heap!

OK, Let's get going!

But first...a quick message

There is a ton of content to take in here...

don't get overwhelmed trying to master it all at once.

I BEG YOU

Learn Singly Linked Lists

TAKE A BREAK!

Learn Doubly Linked Lists

PAY ATTENTION TO THE PREREQUISITES FOR EACH SECTION!

OK, OK I'm done.

Now we just need to learn a bit of ES2015 syntax that we'll use along the way

ES2015

CLASS SYNTAX

OBJECTIVES

  • Explain what a class is
  • Understand how JavaScript implements the idea of classes
  • Define terms like abstraction, encapsulation and polymorphism
  • Use ES2015 classes to implement data structures

What is a class?

Does JavaScript really have them?

Ehh....not really

A blueprint for creating objects with pre-defined properties and methods

Why do we need to learn this?

We're going to implement data structures as classes!

THE SYNTAX

class Student {
    constructor(firstName, lastName){
        this.firstName = firstName;
        this.lastName = lastName;
    }
}

The method to create new objects must be called constructor

The class keyword creates a constant, so you can not redefine it. Watch out for the syntax as well!

Creating objects from classes

We use the new keyword 

class Student {
    constructor(firstName, lastName){
        this.firstName = firstName;
        this.lastName = lastName;
    }
}

let firstStudent = new Student("Colt", "Steele");
let secondStudent = new Student("Blue", "Steele");

Instance Methods

class Student {
    constructor(firstName, lastName){
        this.firstName = firstName;
        this.lastName = lastName;
    }
    fullName(){
        return `Your full name is ${this.firstName} ${this.lastName}`;
    }
}

let firstStudent = new Student("Colt", "Steele");

firstStudent.fullName() // "Colt Steele"

Class Methods

class Student {
    constructor(firstName, lastName){
        this.firstName = firstName;
        this.lastName = lastName;
    }
    
    fullName(){
        return `Your full name is ${this.firstName} ${this.lastName}`;
    }
    
    static enrollStudents(...students){
        // maybe send an email here
    }
}

let firstStudent = new Student("Colt", "Steele");
let secondStudent = new Student("Blue", "Steele");

Student.enrollStudents([firstStudent, secondStudent])

How we'll be using classes

class DataStructure(){
    constructor(){
        // what default properties should it have?
    }
    someInstanceMethod(){
        // what should each object created from this class be able to do?
    }
}

We will almost never be using static methods

We will be using the constructor and instance methods quite a bit!

One gotcha with `this`

Inside all of our instance methods and constructor, the keyword `this` refers to the object created from that class (also known as an instance)

YOUR

TURN

Recap

  • Classes are blueprints that when created make objects known as instances
  • Classes are created with the new keyword
  • The constructor function is a special function that gets run when the class is instantiated
  • Instance methods can be added to classes similar to methods in objects
  • Class methods can be added using the static keyword