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

# Challenge Notebook¶

## Constraints¶

• Can we assume the input is always a positive int?
• Yes
• Can we assume we're working with 32 bits?
• Yes
• Is the output an int?
• Yes
• Can we assume the inputs are valid (not None)?
• No
• Can we assume this fits memory?
• Yes

## Test Cases¶

• None -> Exception
• 0 -> 0
• -1 -> -1
• General case
  input  = 1001 1111 0110
result = 0110 1111 1001

## 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 Bits(object):

def pairwise_swap(self, num):
# TODO: Implement me
pass


## Unit Test¶

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

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

class TestBits(unittest.TestCase):

def test_pairwise_swap(self):
bits = Bits()
self.assertEqual(bits.pairwise_swap(0), 0)
self.assertEqual(bits.pairwise_swap(1), 1)
num = int('0000100111110110', base=2)
expected = int('0000011011111001', base=2)
self.assertEqual(bits.pairwise_swap(num), expected)
print('Success: test_pairwise_swap')

def main():
test = TestBits()
test.test_pairwise_swap()

if __name__ == '__main__':
main()


## Solution Notebook¶

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