feat(book/linkedlist): add applications

Author: amejiarosario

book/content/part02/linked-list.asc

@@ -9,7 +9,28 @@ endif::[]
 [[linked-list]]
 === Linked List
 
-A list (or Linked List) is a linear data structure where each object has a pointer to the next one.
+A list (or Linked List) is a linear data structure where each object has a pointer to the next one creating a chain. You can also have a back reference to the previous node.
+
+image::dllx4-compact.png[]
+
+The data doesn't have to be a number. It can be anything that you need (e.g., images, songs, menu items).
+
+.Some features powered by linked lists:
+- _Image viewer_ – The previous and next images are linked in an image viewer so that the user can navigate them.
+- _Previous and next page in web browser_ – We can access the previous and next URL searched in a web browser by pressing the back and next button since they are linked.
+- _Music Player_ - Queue of songs in a music player connects them so you can move to the next song or previous one.
+
+.Other Applications:
+- Build <<Stack>> and <<Queue>> data structures, which are useful for Graph Traversal and other things.
+- Linked Lists are used on <<hashmap-chap>> to handle collisions.
+- Linked Lists can be used when representing a <<graph>> as an adjacency list.
+- Operate arbitrary big numbers (think hundreds of digits). Each digit is a node of a linked list.
+- Manipulation of polynomials by storing constants in the node of a linked list.
+- Representing sparse matrices (an array representation will waste a lot of memory when most of the cells are empty). The linked list will represent only the non-zero values saving significant space.
+
+Hopefully, this will get you excited about learning Linked Lists since it's the base of many interesting applications. Let's learn more about the different types of linked lists.
+
+==== Types of Linked List
 
 .Linked Lists can be:
 - *Singly*: every item has a pointer to the next.