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

Challenge Notebook¶

Problem: Compress a string such that 'AAABCCDDDD' becomes 'A3BC2D4'. Only compress the string if it saves space.¶

Constraints¶

Can we assume the string is ASCII?
- Yes
- Note: Unicode strings could require special handling depending on your language
Is this case sensitive?
- Yes
Can we use additional data structures?
- Yes
Can we assume this fits in memory?
- Yes

Test Cases¶

None -> None
'' -> ''
'AABBCC' -> 'AABBCC'
'AAABCCDDDD' -> 'A3BC2D4'

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 CompressString(object):

    def compress(self, string):
        # TODO: Implement me
        pass

Unit Test¶

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

In [ ]:

# %load test_compress.py
import unittest


class TestCompress(unittest.TestCase):

    def test_compress(self, func):
        self.assertEqual(func(None), None)
        self.assertEqual(func(''), '')
        self.assertEqual(func('AABBCC'), 'AABBCC')
        self.assertEqual(func('AAABCCDDDDE'), 'A3BC2D4E')
        self.assertEqual(func('BAAACCDDDD'), 'BA3C2D4')
        self.assertEqual(func('AAABAACCDDDD'), 'A3BA2C2D4')
        print('Success: test_compress')


def main():
    test = TestCompress()
    compress_string = CompressString()
    test.test_compress(compress_string.compress)


if __name__ == '__main__':
    main()

Solution Notebook¶

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