This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges).

Challenge Notebook

Problem: Remove duplicates from a linked list

Constraints
Test Cases
Algorithm
Code
Unit Test
Solution Notebook

Constraints

Is this a singly or doubly linked list?
- Singly
Can you insert None values in the list?
- No
Can you use additional data structures?
- Implement both solutions
Can we assume we already have a linked list class that can be used for this problem?
- Yes

Test Cases

Empty linked list -> []
One element linked list -> [element]
General case with no duplicates
General case with duplicates

Algorithm

Refer to the Solution Notebook. If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.

Code



In [ ]:

    
%run ../linked_list/linked_list.py
%load ../linked_list/linked_list.py



In [ ]:

    
class MyLinkedList(LinkedList):

    def remove_dupes(self):
        # TODO: Implement me
        pass

Unit Test

The following unit test is expected to fail until you solve the challenge.



In [ ]:

    
# %load test_remove_duplicates.py
from nose.tools import assert_equal


class TestRemoveDupes(object):

    def test_remove_dupes(self, linked_list):
        print('Test: Empty list')
        linked_list.remove_dupes()
        assert_equal(linked_list.get_all_data(), [])

        print('Test: One element list')
        linked_list.insert_to_front(2)
        linked_list.remove_dupes()
        assert_equal(linked_list.get_all_data(), [2])

        print('Test: General case, duplicates')
        linked_list.insert_to_front(1)
        linked_list.insert_to_front(3)
        linked_list.insert_to_front(1)
        linked_list.insert_to_front(1)
        linked_list.remove_dupes()
        assert_equal(linked_list.get_all_data(), [1, 3, 2])

        print('Test: General case, no duplicates')
        linked_list.remove_dupes()
        assert_equal(linked_list.get_all_data(), [1, 3, 2])

        print('Success: test_remove_dupes\n')


def main():
    test = TestRemoveDupes()
    linked_list = MyLinkedList(None)
    test.test_remove_dupes(linked_list)


if __name__ == '__main__':
    main()

Solution Notebook

Review the Solution Notebook for a discussion on algorithms and code solutions.