#!/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: Determine if a linked list is a palindrome.
# 
# * [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
# * Is a single character or number a palindrome?
#     * No
# * Can we assume we already have a linked list class that can be used for this problem?
#     * Yes
# * Can we use additional data structures?
#     * Yes
# * Can we assume this fits in memory?
#     * Yes

# ## Test Cases
# 
# 
# * Empty list -> False
# * Single element list -> False
# * Two or more element list, not a palindrome -> False
# * General case: Palindrome with even length -> True
# * General case: Palindrome with odd length -> True

# ## Algorithm
# 
# Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/palindrome/palindrome_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 is_palindrome(self):
        # TODO: Implement me
        pass


# ## Unit Test

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

# In[ ]:


# %load test_palindrome.py
import unittest


class TestPalindrome(unittest.TestCase):

    def test_palindrome(self):
        print('Test: Empty list')
        linked_list = MyLinkedList()
        self.assertEqual(linked_list.is_palindrome(), False)

        print('Test: Single element list')
        head = Node(1)
        linked_list = MyLinkedList(head)
        self.assertEqual(linked_list.is_palindrome(), False)

        print('Test: Two element list, not a palindrome')
        linked_list.append(2)
        self.assertEqual(linked_list.is_palindrome(), False)

        print('Test: General case: Palindrome with even length')
        head = Node('a')
        linked_list = MyLinkedList(head)
        linked_list.append('b')
        linked_list.append('b')
        linked_list.append('a')
        self.assertEqual(linked_list.is_palindrome(), True)

        print('Test: General case: Palindrome with odd length')
        head = Node(1)
        linked_list = MyLinkedList(head)
        linked_list.append(2)
        linked_list.append(3)
        linked_list.append(2)
        linked_list.append(1)
        self.assertEqual(linked_list.is_palindrome(), True)

        print('Success: test_palindrome')


def main():
    test = TestPalindrome()
    test.test_palindrome()


if __name__ == '__main__':
    main()


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