This notebook was prepared by Donne Martin. Source and license info is on GitHub.

Challenge Notebook

Problem: Remove duplicates from a linked list.

Constraints

  • Can we assume this is a non-circular, singly linked list?
    • Yes
  • Can you insert None values in the list?
    • No
  • Can we assume we already have a linked list class that can be used for this problem?
    • Yes
  • Can we use additional data structures?
    • Implement both solutions
  • Can we assume this fits in memory?
    • 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
import unittest


class TestRemoveDupes(unittest.TestCase):

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

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

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

        print('Test: General case, no duplicates')
        linked_list.remove_dupes()
        self.assertEqual(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.