59 lines
1.9 KiB
Markdown
59 lines
1.9 KiB
Markdown
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# Linked List
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Implement a doubly linked list.
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Like an array, a linked list is a simple linear data structure. Several
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common data types can be implemented using linked lists, like queues,
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stacks, and associative arrays.
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A linked list is a collection of data elements called *nodes*. In a
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*singly linked list* each node holds a value and a link to the next node.
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In a *doubly linked list* each node also holds a link to the previous
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node.
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You will write an implementation of a doubly linked list. Implement a
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Node to hold a value and pointers to the next and previous nodes. Then
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implement a List which holds references to the first and last node and
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offers an array-like interface for adding and removing items:
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* `push` (*insert value at back*);
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* `pop` (*remove value at back*);
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* `shift` (*remove value at front*).
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* `unshift` (*insert value at front*);
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To keep your implementation simple, the tests will not cover error
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conditions. Specifically: `pop` or `shift` will never be called on an
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empty list.
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If you want to know more about linked lists, check [Wikipedia](https://en.wikipedia.org/wiki/Linked_list).
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* * * *
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For installation and learning resources, refer to the
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[Ruby resources page](http://exercism.io/languages/ruby/resources).
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For running the tests provided, you will need the Minitest gem. Open a
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terminal window and run the following command to install minitest:
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gem install minitest
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If you would like color output, you can `require 'minitest/pride'` in
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the test file, or note the alternative instruction, below, for running
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the test file.
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Run the tests from the exercise directory using the following command:
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ruby linked_list_test.rb
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To include color from the command line:
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ruby -r minitest/pride linked_list_test.rb
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## Source
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Classic computer science topic
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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