#!/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: Invert a binary tree.
# 
# * [Constraints](#Constraints)
# * [Test Cases](#Test-Cases)
# * [Algorithm](#Algorithm)
# * [Code](#Code)
# * [Unit Test](#Unit-Test)
# * [Solution Notebook](#Solution-Notebook)

# ## Constraints
# 
# * What does it mean to invert a binary tree?
#     * Swap all left and right node pairs
# * Can we assume we already have a Node class?
#     * Yes
# * Can we assume the inputs are valid?
#     * No
# * Can we assume this fits memory?
#     * Yes

# ## Test Cases
# 
# <pre>
# Input:
#      5
#    /   \
#   2     7
#  / \   / \
# 1   3 6   9
# 
# Output:
#      5
#    /   \
#   7     2
#  / \   / \
# 9   6 3   1
# </pre>

# ## Algorithm
# 
# Refer to the [Solution Notebook](http://nbviewer.jupyter.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/invert_tree/invert_tree_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', '../bst/bst.py')


# In[ ]:


class InverseBst(Bst):

    def invert_tree(self):
        # TODO: Implement me
        pass


# ## Unit Test

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

# In[ ]:


# %load test_invert_tree.py
import unittest


class TestInvertTree(unittest.TestCase):

    def test_invert_tree(self):
        root = Node(5)
        bst = InverseBst(root)
        node2 = bst.insert(2)
        node3 = bst.insert(3)
        node1 = bst.insert(1)
        node7 = bst.insert(7)
        node6 = bst.insert(6)
        node9 = bst.insert(9)
        result = bst.invert_tree()
        self.assertEqual(result, root)
        self.assertEqual(result.left, node7)
        self.assertEqual(result.right, node2)
        self.assertEqual(result.left.left, node9)
        self.assertEqual(result.left.right, node6)
        self.assertEqual(result.right.left, node3)
        self.assertEqual(result.right.right, node1)
        print('Success: test_invert_tree')


def main():
    test = TestInvertTree()
    test.test_invert_tree()


if __name__ == '__main__':
    main()


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