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, so you don’t have to think about overcoming that limitation.
So if array size is not a limitation 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.
Structure of a Linked List
A linked list is a linear collection of data elements called nodes that “point” to the next node by means of a pointer.
Each node holds a single element of data and a link or pointer to the next node in the list.
A head node is the first node in the list, a tail node is the last node in the list. Below is a basic representation of a linked list:
[ NODE(head) ] -> [ NODE ] -> [ NODE(tail) ] -> nil
For a more thorough explanation, use these resources:
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.