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

# Challenge Notebook¶

## Constraints¶

• Can the input have duplicates?
• Yes
• Can the output have duplicates?
• No
• Is the output a list of strings?
• Yes
• Do we have to output the results in sorted order?
• No
• Can we assume the inputs are valid?
• No
• Can we assume this fits memory?
• Yes

## Test Cases¶

* None -> None
* '' -> ''
* 'AABC' -> ['AABC', 'AACB', 'ABAC', 'ABCA',
'ACAB', 'ACBA', 'BAAC', 'BACA',
'BCAA', 'CAAB', 'CABA', 'CBAA']


## 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 find_permutations(self, string):
# TODO: Implement me
pass


## Unit Test¶

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

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

class TestPermutations(unittest.TestCase):

def test_permutations(self):
permutations = Permutations()
self.assertEqual(permutations.find_permutations(None), None)
self.assertEqual(permutations.find_permutations(''), '')
string = 'AABC'
expected = [
'AABC', 'AACB', 'ABAC', 'ABCA',
'ACAB', 'ACBA', 'BAAC', 'BACA',
'BCAA', 'CAAB', 'CABA', 'CBAA'
]
self.assertEqual(permutations.find_permutations(string), expected)
print('Success: test_permutations')

def main():
test = TestPermutations()
test.test_permutations()

if __name__ == '__main__':
main()


## Solution Notebook¶

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