Data Structures and Algorithms

muigai unaka

Week 4

Stack

A Last-In-First-Out data structure that is a common use of an array. Think of a stack of plates in your cupboard, new plates are added on top of the previous plates and to get a plate, you would remove the top plate

Stack

Add to a stack using .push()

Stack

let stack = [];
stack.push(3)

Remove from a stack using .pop()

let stack = []; stack.push(3); stack.push(2); stack.push(1);
stack.pop(); // removes 1, which was the last added element

Get item that is at the top of the Stack
Add item to the top of the Stack
Implement a Queue using a Stack
Depth First Search
Pre-order, In-order, Post-order traversal of a binary tree

Common Operations with Stack

Queue

A First-In-First-Out data structure that is a common use of an array. Think of a single register line at the movie theater, new people are added to the end or taken from the beginning once they have their ticket

Queue

Add to a queue using .push()

Queue

let queue = [];
queue.push(1)

Remove from a queue using .shift()

let queue = []; queue.push(1); queue.push(2);
queue.shift(); // removes 1 from the beginning

Get item that is at the front of the Queue
Add item to the end of the Queue
Implement a Stack using a Queue
Breadth First Search
Level Order Traversal

Common Operations with Queue

ጥያቄዎች?

(t’iyak’ēwochi)

Linked List

A sequence data structure, which connects elements, called nodes, through links. Nodes in a linked list are connected by pointers. Linked lists are null terminating, which means whenever the pointer to the next node is null, the list has reached the end.

Linked List

When you think of a Linked List, a real world example would be a music playlist. The first song in the playlist would be the head. It connects to the next song and each song has a reference to a previous and next song. You know you've reached the end of the playlist when there is no next song.

Linked List

// To create a Linked List you will need "Nodes"
// Nodes will have data and a reference to the next Node
function Node (data) {
  this.data = data;
  // every node starts off with their next set to null
  this.next = null;
}

let head = new Node(1);
// We "link" lists by reassigning the next value of a node
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(true);
head.next.next.next.next = new Node({ 
  fun_fact: "Linked Lists can store any data" 
})

let LinkedList = head;