This notebook was prepared by Donne Martin. Source and license info is on GitHub.
input = 0000 1001 1111 0110 result = 0000 0110 1111 1001
* Isolate the odd bits with a mask: 0000 1001 1111 0110 num 1010 1010 1010 1010 mask -------------------------------- 0000 1000 1010 0010 num & mask * Shift the odd bits right: 0000 0100 0101 0001 odd * Isolate the even bits with a mask: 0000 1001 1111 0110 num 0101 0101 0101 0101 mask -------------------------------- 0000 0001 0101 0100 num & mask * Shift the even bits left: 0000 0010 1010 1000 even * Return even | odd 0000 0100 0101 0001 odd 0000 0010 1010 1000 even -------------------------------- 0000 0110 1111 1001 odd | even
Complexity:
class Bits(object):
def pairwise_swap(self, num):
if num is None:
raise TypeError('num cannot be None')
if num == 0 or num == 1:
return num
odd = (num & int('1010101010101010', base=2)) >> 1
even = (num & int('0101010101010101', base=2)) << 1
return odd | even
%%writefile 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)
self.assertRaises(TypeError, bits.pairwise_swap, None)
print('Success: test_pairwise_swap')
def main():
test = TestBits()
test.test_pairwise_swap()
if __name__ == '__main__':
main()
Overwriting test_pairwise_swap.py
%run -i test_pairwise_swap.py
Success: test_pairwise_swap