Linked Lists

A linked list is a linear data structure where each element is a separate object.

{val: 1, next: 
  {val: 2, next: 
    {val:3, next:null}
  }
}

A Sequence of Singly-Linked List Items

Diagram Me!

Singly Linked List:

-- is a data structure which holds a sequence of nodes.

-- each node contains data, and a pointer to another node

nodes can be ANYWHERE in memory, diagram is for mental model only

Why linked lists?

- Efficient -- Easy to add new nodes without needing to change the size of an array.

Arrays are contiguous blocks of memory...

Scavenger Hunt

-- Each node can be thought of as a location in a scavenger hunt. Each location has some data, and points you to the next location.

Your Turn!

Write a function that takes in an array, and creates a singly linked list for any inputArr length

function createSimpleLinkedList (inputArr) {
  // some code
}
createSimpleLinkedList([1,2,3])

=> { val: 1, next: { val: 2, next: { val: 3, next: {} } } }

Solution To Simple Singly Linked List

Write a function that takes in an array, and creates a singly linked list

function createSimpleLinkedList (inputArr) {
  var list = {};
  for (i = inputArr.length - 1 ; i >= 0 ; i--) {
    list = {val:inputArr[i], next:list};
  } // END FOR LOOP
  return list;
} // END FUNCTION

Singly Linked List Using Constructors:

2 Components

1. A prototype for a singlyList

2. A prototype for a Node

Both are needed to construct a functional list.

Anatomy of a Singly Linked List

// create a new list
list = new SinglyLinkedList();
// { head: null, tail: null, length: 0 }

// push a new node to the list
list.push(5)
  // {
  //  head: Node { val: 5, next: null },
  //  tail: Node { val: 5, next: null },
  //  length: 1 
  // }

create a new list, and add a single node

Take a Guess!

What is the space and runtime complexity of inserting into the tail of a linked list?

Anatomy of a Linked List

5 Min Break!

Doubly linked lists

A doubly linked list is a list that has two references, one to the next node and another to previous node

Singly Linked List Using Constructors:

Still 2 Components

!!

How a Node is Constructed in a Doubly Linked List

Adding a node to the doubly linked list

Pushing a new node onto the tails of a doubly linked list

Double Linked List in action

list = new DoublyLinkedList();
// { head: null, tail: null, length: 0 }

list.push(5);
 // {
 //    head: Node { val: 5, next: null, prev: null },
 //    tail: Node { val: 5, next: null, prev: null },
 //    length: 1
 //  }

list.push(8);

// {
//   head:
//    Node {
//      val: 5,
//      next: Node { val: 8, next: null, prev: [Circular] },
//      prev: null },
//   tail:
//    Node {
//      val: 8,
//      next: null,
//      prev: Node { val: 5, next: [Circular], prev: null } },
//   length: 2 
// }

Linked List Facts:

• The DOM is a linked List(graph)!

  • ​node.nextSibling, node.parentNode...

• ​Linked Lists are NOT indexed

• Linked Lists DON'T support arbitrary access

• Adding removing from a Linked List is often faster!

• Wiki on tradoffs for linked lists

Go forth and link some lists!