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

Challenge Notebook

Problem: Find the difference of two integers without using the + or - sign.

Constraints

  • Can we assume the inputs are valid?
    • No, check for None
  • Can we assume this fits memory?
    • Yes

Test Cases

* None input -> TypeError
* 7, 5 -> 2
* -5, -7 -> 2
* -5, 7 -> -12
* 5, -7 -> 12

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 sub_two(self, val):
        # TODO: Implement me
        pass

Unit Test

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

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


class TestSubTwo(unittest.TestCase):

    def test_sub_two(self):
        solution = Solution()
        self.assertRaises(TypeError, solution.sub_two, None)
        self.assertEqual(solution.sub_two(7, 5), 2)
        self.assertEqual(solution.sub_two(-5, -7), 2)
        self.assertEqual(solution.sub_two(-5, 7), -12)
        self.assertEqual(solution.sub_two(5, -7), 12)
        print('Success: test_sub_two')


def main():
    test = TestSubTwo()
    test.test_sub_two()


if __name__ == '__main__':
    main()

Solution Notebook

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