#!/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).

# # Challenge Notebook

# ## Problem: Implement radix sort.
# 
# * [Constraints](#Constraints)
# * [Test Cases](#Test-Cases)
# * [Algorithm](#Algorithm)
# * [Code](#Code)
# * [Unit Test](#Unit-Test)
# * [Solution Notebook](#Solution-Notebook)

# ## Constraints
# 
# * Is the input a list?
#     * Yes
# * Can we assume the inputs are valid?
#     * Check for None in place of an array
#     * Assume array elements are ints
# * Do we know the max digits to handle?
#     * No
# * Are the digits base 10?
#     * Yes
# * Can we assume this fits memory?
#     * Yes

# ## Test Cases
# 
# * None -> Exception
# * [] -> []
# * [128, 256, 164, 8, 2, 148, 212, 242, 244] -> [2, 8, 128, 148, 164, 212, 242, 244, 256]

# ## Algorithm
# 
# Refer to the [Solution Notebook](http://nbviewer.jupyter.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/radix_sort/radix_sort_solution.ipynb).  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.

# ## Code

# In[ ]:


class RadixSort(object):

    def sort(self, array, base=10):
        # TODO: Implement me
        pass


# ## Unit Test

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

# In[ ]:


# %load test_radix_sort.py
import unittest


class TestRadixSort(unittest.TestCase):

    def test_sort(self):
        radix_sort = RadixSort()
        self.assertRaises(TypeError, radix_sort.sort, None)
        self.assertEqual(radix_sort.sort([]), [])
        array = [128, 256, 164, 8, 2, 148, 212, 242, 244]
        expected = [2, 8, 128, 148, 164, 212, 242, 244, 256]
        self.assertEqual(radix_sort.sort(array), expected)
        print('Success: test_sort')


def main():
    test = TestRadixSort()
    test.test_sort()


if __name__ == '__main__':
    main()


# ## Solution Notebook
# 
# Review the [Solution Notebook]() for a discussion on algorithms and code solutions.