exercism/ruby/linked-list

Linked List

Implement a doubly linked list.

Like an array, a linked list is a simple linear data structure. Several common data types can be implemented using linked lists, like queues, stacks, and associative arrays.

A linked list is a collection of data elements called nodes. In a singly linked list each node holds a value and a link to the next node. In a doubly linked list each node also holds a link to the previous node.

You will write an implementation of a doubly linked list. Implement a Node to hold a value and pointers to the next and previous nodes. Then implement a List which holds references to the first and last node and offers an array-like interface for adding and removing items:

• push (insert value at back);
• pop (remove value at back);
• shift (remove value at front).
• unshift (insert value at front);

To keep your implementation simple, the tests will not cover error conditions. Specifically: pop or shift will never be called on an empty list.

If you want to know more about linked lists, check Wikipedia.

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For installation and learning resources, refer to the Ruby resources page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby linked_list_test.rb

To include color from the command line:

ruby -r minitest/pride linked_list_test.rb

Source

Classic computer science topic

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.