#!/usr/bin/env python
# coding: utf-8

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

# # Solution Notebook

# ## Problem: Given a real number between 0 and 1, print the binary representation.  If the length of the representation is > 32, return 'ERROR'.
# 
# * [Constraints](#Constraints)
# * [Test Cases](#Test-Cases)
# * [Algorithm](#Algorithm)
# * [Code](#Code)
# * [Unit Test](#Unit-Test)

# ## 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]:


get_ipython().run_cell_magic('writefile', 'test_print_binary.py', "import unittest\n\n\nclass TestBits(unittest.TestCase):\n\n    def test_print_binary(self):\n        bit = Bits()\n        self.assertEqual(bit.print_binary(None), 'ERROR')\n        self.assertEqual(bit.print_binary(0), 'ERROR')\n        self.assertEqual(bit.print_binary(1), 'ERROR')\n        num = 0.625\n        expected = '0.101'\n        self.assertEqual(bit.print_binary(num), expected)\n        num = 0.987654321\n        self.assertEqual(bit.print_binary(num), 'ERROR')\n        print('Success: test_print_binary')\n\n\ndef main():\n    test = TestBits()\n    test.test_print_binary()\n\n\nif __name__ == '__main__':\n    main()\n")


# In[3]:


get_ipython().run_line_magic('run', '-i test_print_binary.py')