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

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

# # Challenge Notebook

# ## Problem: Add two numbers whose digits are stored in a linked list in reverse order.
# 
# * [Constraints](#Constraints)
# * [Test Cases](#Test-Cases)
# * [Algorithm](#Algorithm)
# * [Code](#Code)
# * [Unit Test](#Unit-Test)
# * [Solution Notebook](#Solution-Notebook)

# ## Constraints
# 
# * Can we assume this is a non-circular, singly linked list?
#     * Yes
# * Do we expect the return to be in reverse order too?
#     * Yes
# * What if one of the inputs is None?
#     * Return None for an invalid operation
# * How large are these numbers--can they fit in memory?
#     * Yes
# * Can we assume we already have a linked list class that can be used for this problem?
#     * Yes
# * Can we assume this fits in memory?
#     * Yes

# ## Test Cases
# 
# * Empty list(s) -> None
# * Add values of different lengths
#     * Input 1: 6->5->None
#     * Input 2: 9->8->7
#     * Result: 5->4->8
# * Add values of same lengths
#     * Exercised from values of different lengths
#     * Done here for completeness

# ## Algorithm
# 
# Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/add_reverse/add_reverse_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[ ]:


get_ipython().run_line_magic('run', '../linked_list/linked_list.py')
get_ipython().run_line_magic('load', '../linked_list/linked_list.py')


# In[ ]:


class MyLinkedList(LinkedList):

    def add_reverse(self, first_list, second_list):
        # TODO: Implement me
        pass


# ## Unit Test

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

# In[ ]:


# %load test_add_reverse.py
import unittest


class TestAddReverse(unittest.TestCase):

    def test_add_reverse(self):
        print('Test: Empty list(s)')
        self.assertEqual(MyLinkedList().add_reverse(None, None), None)
        self.assertEqual(MyLinkedList().add_reverse(Node(5), None), None)
        self.assertEqual(MyLinkedList().add_reverse(None, Node(10)), None)

        print('Test: Add values of different lengths')
        # Input 1: 6->5->None
        # Input 2: 9->8->7
        # Result: 5->4->8
        first_list = MyLinkedList(Node(6))
        first_list.append(5)
        second_list = MyLinkedList(Node(9))
        second_list.append(8)
        second_list.append(7)
        result = MyLinkedList().add_reverse(first_list, second_list)
        self.assertEqual(result.get_all_data(), [5, 4, 8])

        print('Test: Add values of same lengths')
        # Input 1: 6->5->4
        # Input 2: 9->8->7
        # Result: 5->4->2->1
        first_head = Node(6)
        first_list = MyLinkedList(first_head)
        first_list.append(5)
        first_list.append(4)
        second_head = Node(9)
        second_list = MyLinkedList(second_head)
        second_list.append(8)
        second_list.append(7)
        result = MyLinkedList().add_reverse(first_list, second_list)
        self.assertEqual(result.get_all_data(), [5, 4, 2, 1])

        print('Success: test_add_reverse')


def main():
    test = TestAddReverse()
    test.test_add_reverse()


if __name__ == '__main__':
    main()


# ## Solution Notebook
# 
# Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/add_reverse/add_reverse_solution.ipynb) for a discussion on algorithms and code solutions.