In Computer Science, one of the most basic and fundamental data structures is the linked list, which functions similarly to an array. The principal benefit of a linked list over a conventional array is that the list elements can easily be inserted or removed without reallocation of any other elements.
In some programming languages, the size of an array is a concern and one of the ways to overcome that problem and allow dynamically allocated data is using linked lists.
Luckily in Ruby, arrays aren’t limited to a certain size, and both insertion and deletion can be done trivially at any index using the appropriate built in array method, so you don’t have to think about overcoming those limitations.
So if array size, array insertion and array deletion are not limitations in Ruby, are linked lists really necessary? The short answer to that is no; however, it’s the simplest of the dynamic data structures and it will give you a solid foundation, so you can understand more complex data structures like graphs and binary trees with more ease.
You will need two classes:
LinkedListclass, which will represent the full list.
Nodeclass, containing a
#valuemethod and a link to the
#next_node, set both as
Build the following methods in your linked list class:
#append(value)adds a new node containing
valueto the end of the list
#prepend(value)adds a new node containing
valueto the start of the list
#sizereturns the total number of nodes in the list
#headreturns the first node in the list
#tailreturns the last node in the list
#at(index)returns the node at the given
#popremoves the last element from the list
#contains?(value)returns true if the passed in value is in the list and otherwise returns false.
#find(value)returns the index of the node containing value, or nil if not found.
#to_srepresent your LinkedList objects as strings, so you can print them out and preview them in the console. The format should be:
( value ) -> ( value ) -> ( value ) -> nil
#insert_at(value, index)that inserts a new node with the provided
valueat the given
#remove_at(index)that removes the node at the given
Extra Credit Tip: When you insert or remove a node, consider how it will affect the existing nodes. Some of the nodes will need their
#next_node link updated.