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

Challenge Notebook¶

Problem: Determine if a string is a permutation of another string.¶

Constraints¶

Can we assume the string is ASCII?
- Yes
- Note: Unicode strings could require special handling depending on your language
Is whitespace important?
- Yes
Is this case sensitive? 'Nib', 'bin' is not a match?
- Yes
Can we use additional data structures?
- Yes
Can we assume this fits in memory?
- Yes

Test Cases¶

One or more None inputs -> False
One or more empty strings -> False
'Nib', 'bin' -> False
'act', 'cat' -> True
'a ct', 'ca t' -> True

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 Permutations(object):

    def is_permutation(self, str1, str2):
        # TODO: Implement me
        pass

Unit Test¶

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

In [ ]:

# %load test_permutation_solution.py
import unittest


class TestPermutation(unittest.TestCase):

    def test_permutation(self, func):
        self.assertEqual(func(None, 'foo'), False)
        self.assertEqual(func('', 'foo'), False)
        self.assertEqual(func('Nib', 'bin'), False)
        self.assertEqual(func('act', 'cat'), True)
        self.assertEqual(func('a ct', 'ca t'), True)
        self.assertEqual(func('dog', 'doggo'), False)
        print('Success: test_permutation')


def main():
    test = TestPermutation()
    permutations = Permutations()
    test.test_permutation(permutations.is_permutation)
    try:
        permutations_alt = PermutationsAlt()
        test.test_permutation(permutations_alt.is_permutation)
    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.