Learn How to Code

Project: Linked Lists

Learning how nodes work by writing them, and building a linked list, will give you a solid understanding for learning about a more complex subject in the next section, trees.


In our previous lesson, we looked at Nodes, Linked Lists and Trees; the latter two being core data structures to add to your repetoire, and Nodes being the foundation those data structures are built upon.
As stated previously, if your language of choice is Ruby or JavaScript, in practice you won't have to concern yourself with implementing Linked Lists as Arrays are not a fixed sized in these languages. However, learning how Nodes work by writing them, and building a Linked List with them; will give you a working understanding of how Linked Lists work, and give you a solid, founding principle for tackling the bigger task ahead...

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:


In your language of choice...
You will need two classes:
  1. 1.
    LinkedList class, which will represent the full list.
  2. 2.
    Node class, containing a #value method and a link to the #next_node, set both as nil by default.
Build the following methods in your linked list class:
  1. 1.
    #append(value) adds a new node containing value to the end of the list
  2. 2.
    #prepend(value) adds a new node containing value to the start of the list
  3. 3.
    #size returns the total number of nodes in the list
  4. 4.
    #head returns the first node in the list
  5. 5.
    #tail returns the last node in the list
  6. 6.
    #at(index) returns the node at the given index
  7. 7.
    #pop removes the last element from the list
  8. 8.
    #contains?(value) returns true if the passed in value is in the list and otherwise returns false.
  9. 9.
    #find(value) returns the index of the node containing value, or nil if not found.
  10. 10.
    #to_s represent 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

Extra credit

  1. 1.
    #insert_at(value, index) that inserts the node with the provided value at the given index
  2. 2.
    #remove_at(index) that removes the node at the given index. (You will need to update the links of your nodes in the list when you remove a node.)