#!/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: Delete a node in the middle, given only access to that node.
# 
# * [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
# * What if the final node is being deleted, do we make it a dummy with value None?
#     * Yes
# * Can we assume we already have a linked list class that can be used for this problem?
#     * Yes

# ## Test Cases
# 
# * Delete on empty list -> None
# * Delete None -> None
# * Delete on one node -> [None]
# * Delete on multiple nodes

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


# ## Unit Test

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

# In[ ]:


# %load test_delete_mid.py
import unittest


class TestDeleteNode(unittest.TestCase):

    def test_delete_node(self):
        print('Test: Empty list, null node to delete')
        linked_list = MyLinkedList(None)
        linked_list.delete_node(None)
        self.assertEqual(linked_list.get_all_data(), [])

        print('Test: One node')
        head = Node(2)
        linked_list = MyLinkedList(head)
        linked_list.delete_node(head)
        self.assertEqual(linked_list.get_all_data(), [None])

        print('Test: Multiple nodes')
        linked_list = MyLinkedList(None)
        node0 = linked_list.insert_to_front(2)
        node1 = linked_list.insert_to_front(3)
        node2 = linked_list.insert_to_front(4)
        node3 = linked_list.insert_to_front(1)
        linked_list.delete_node(node1)
        self.assertEqual(linked_list.get_all_data(), [1, 4, 2])

        print('Test: Multiple nodes, delete last element')
        linked_list = MyLinkedList(None)
        node0 = linked_list.insert_to_front(2)
        node1 = linked_list.insert_to_front(3)
        node2 = linked_list.insert_to_front(4)
        node3 = linked_list.insert_to_front(1)
        linked_list.delete_node(node0)
        self.assertEqual(linked_list.get_all_data(), [1, 4, 3, None])

        print('Success: test_delete_node')


def main():
    test = TestDeleteNode()
    test.test_delete_node()


if __name__ == '__main__':
    main()


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