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

Challenge Notebook

Problem: Move all zeroes in a list to the end.

Constraints

  • Is the input an array of ints?
    • Yes
  • Is the output a new array of ints?
    • No, do this in-place
  • Do we need to maintain ordering of non-zero values?
    • Yes
  • Can we assume the inputs are valid?
    • No
  • Can we assume this fits memory?
    • Yes

Test Cases

* None -> TypeError
* [0, 1, 0, 3, 12]
* [1, 0] -> [1, 0]
* [0, 1] -> [1, 0]
* [0] -> [0]
* [1] -> [1]
* [1, 1] -> [1, 1]

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 Solution(object):

    def move_zeroes(self, nums):
        # TODO: Implement me
        pass

Unit Test

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

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


class TestMoveZeroes(unittest.TestCase):

    def test_move_zeroes(self):
        solution = Solution()
        self.assertRaises(TypeError, solution.move_zeroes, None)
        array = [0, 1, 0, 3, 12]
        solution.move_zeroes(array)
        self.assertEqual(array, [1, 3, 12, 0, 0])
        array = [1, 0]
        solution.move_zeroes(array)
        self.assertEqual(array, [1, 0])
        array = [0, 1]
        solution.move_zeroes(array)
        self.assertEqual(array, [1, 0])
        array = [0]
        solution.move_zeroes(array)
        self.assertEqual(array, [0])
        array = [1]
        solution.move_zeroes(array)
        self.assertEqual(array, [1])
        array = [1, 1]
        solution.move_zeroes(array)
        self.assertEqual(array, [1, 1])
        print('Success: test_move_zeroes')


def main():
    test = TestMoveZeroes()
    test.test_move_zeroes()


if __name__ == '__main__':
    main()

Solution Notebook

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