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

Challenge Notebook

Problem: Implement selection sort.

Constraints

  • Is a naive solution sufficient (ie not stable, not based on a heap)?
    • Yes
  • Are duplicates allowed?
    • Yes
  • Can we assume the input is valid?
    • No
  • Can we assume this fits memory?
    • Yes

Test Cases

  • None -> Exception
  • Empty input -> []
  • One element -> [element]
  • Two or more elements

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 [ ]:
class SelectionSort(object):

    def sort(self, data):
        # TODO: Implement me (recursive)
        pass

Unit Test

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

In [ ]:
# %load test_selection_sort.py
import unittest


class TestSelectionSort(unittest.TestCase):

    def test_selection_sort(self, func):
        print('None input')
        self.assertRaises(TypeError, func, None)

        print('Empty input')
        self.assertEqual(func([]), [])

        print('One element')
        self.assertEqual(func([5]), [5])

        print('Two or more elements')
        data = [5, 1, 7, 2, 6, -3, 5, 7, -10]
        self.assertEqual(func(data), sorted(data))

        print('Success: test_selection_sort\n')


def main():
    test = TestSelectionSort()
    selection_sort = SelectionSort()
    test.test_selection_sort(selection_sort.sort)
    try:
        test.test_selection_sort(selection_sort.sort_recursive)
        test.test_selection_sort(selection_sort.sor_iterative_alt)
    except NameError:
        # Alternate solutions are only defined
        # in the solutions file
        pass


if __name__ == '__main__':
    main()

Solution Notebook

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