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

Solution Notebook

Problem: Maximizing XOR

See the HackerRank problem page.

Constraints
Test Cases
Algorithm
Code
Unit Test

Constraints

See the HackerRank problem page.

Test Cases

See the HackerRank problem page.

Algorithm

Set max to 0
For i in the range (lower, upper) inclusive
- For j in the range (lower, upper) inclusive
  - Compare i ^ j with max, update max if needed
return max

Complexity:

Time: O(n^2) - See note below
Space: O(1)

Note:

TODO: Add more optimal solutions such as those discussed here.

Code



In [1]:

    
def max_xor(lower, upper):
    result = 0
    for l in range(lower, upper + 1):
        for u in range(lower, upper + 1):
            curr = l ^ u
            if result < curr:
                result = curr
    return result

Unit Test



In [2]:

    
%%writefile test_maximizing_xor.py
from nose.tools import assert_equal


class TestMaximingXor(object):

    def test_maximizing_xor(self):
        assert_equal(max_xor(10, 15), 7)
        print('Success: test_maximizing_xor')


def main():
    test = TestMaximingXor()
    test.test_maximizing_xor()


if __name__ == '__main__':
    main()









    



Overwriting test_maximizing_xor.py



In [3]:

    
%run -i test_maximizing_xor.py









    



Success: test_maximizing_xor