This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges).

Challenge Notebook

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

Constraints
Test Cases
Algorithm
Code
Unit Test
Solution Notebook

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

Test Cases

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 [ ]:

    
def permutations(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
from nose.tools import assert_equal


class TestPermutation(object):

    def test_permutation(self, func):
        assert_equal(func('', 'foo'), False)
        assert_equal(func('Nib', 'bin'), False)
        assert_equal(func('act', 'cat'), True)
        assert_equal(func('a ct', 'ca t'), True)
        print('Success: test_permutation')


def main():
    test = TestPermutation()
    test.test_permutation(permutations)
    try:
        test.test_permutation(permutations_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.