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

# Solution Notebook¶

## Constraints¶

• Is the input a float?
• Yes
• Is the output a string?
• Yes
• Is 0 and 1 inclusive?
• No
• Does the result include a trailing zero and decimal point?
• Yes
• Is the leading zero and decimal point counted in the 32 char limit?
• Yes
• Can we assume the inputs are valid?
• No
• Can we assume this fits memory?
• Yes

## Test Cases¶

• None -> 'ERROR'
• Out of bounds (0, 1) -> 'ERROR'
• General case
• 0.625 -> 0.101
• 0.987654321 -> 'ERROR'

## Algorithm¶

• Set the result to '0.'
• Start with a fraction of 0.5, which is 0.1 in base 2
• Loop while num > 0
• Check num versus fraction
• If num > fraction, add a 1 to the result, num -= fraction
• Else, add a 0 to the result
• If the len(result) > 32, return 'ERROR'

Complexity:

• Time: O(1)
• Space: O(1)

## Code¶

In [1]:
from __future__ import division

class Bits(object):

MAX_BITS = 32

def print_binary(self, num):
if num is None or num >= 1 or num <= 0:
return 'ERROR'
result = ['0', '.']
fraction = 0.5
while num:
if num >= fraction:
result.append('1')
num -= fraction
else:
result.append('0')
if len(result) > self.MAX_BITS:
return 'ERROR'
fraction /= 2
return ''.join(result)


## Unit Test¶

In [2]:
%%writefile test_print_binary.py
import unittest

class TestBits(unittest.TestCase):

def test_print_binary(self):
bit = Bits()
self.assertEqual(bit.print_binary(None), 'ERROR')
self.assertEqual(bit.print_binary(0), 'ERROR')
self.assertEqual(bit.print_binary(1), 'ERROR')
num = 0.625
expected = '0.101'
self.assertEqual(bit.print_binary(num), expected)
num = 0.987654321
self.assertEqual(bit.print_binary(num), 'ERROR')
print('Success: test_print_binary')

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

if __name__ == '__main__':
main()

Overwriting test_print_binary.py

In [3]:
%run -i test_print_binary.py

Success: test_print_binary