This notebook was prepared by Donne Martin. Source and license info is on GitHub.

# Challenge Notebook¶

## Constraints¶

• If there is no successor, do we return None?
• Yes
• If the input is None, should we throw an exception?
• Yes
• Can we assume we already have a Node class that keeps track of parents?
• Yes
• Can we assume this fits memory?
• Yes

## Test Cases¶

          _5_
/     \
3       8
/ \    /   \
2   4  6    12
/        \   / \
1          7 10  15
/
9

In: None  Out: Exception
In: 4     Out: 5
In: 5     Out: 6
In: 8     Out: 9
In: 15    Out: None


## Algorithm¶

Refer to the Solution Notebook. If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.

## Code¶

In [ ]:
%run ../bst/bst.py

In [ ]:
class BstSuccessor(object):

def get_next(self, node):
# TODO: Implement me
pass


## Unit Test¶

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

In [ ]:
# %load test_bst_successor.py
import unittest

class TestBstSuccessor(unittest.TestCase):

def test_bst_successor_empty(self):
bst_successor = BstSuccessor()
bst_successor.get_next(None)

def test_bst_successor(self):
nodes = {}
node = Node(5)
nodes[5] = node
bst = Bst(nodes[5])
nodes[3] = bst.insert(3)
nodes[8] = bst.insert(8)
nodes[2] = bst.insert(2)
nodes[4] = bst.insert(4)
nodes[6] = bst.insert(6)
nodes[12] = bst.insert(12)
nodes[1] = bst.insert(1)
nodes[7] = bst.insert(7)
nodes[10] = bst.insert(10)
nodes[15] = bst.insert(15)
nodes[9] = bst.insert(9)

bst_successor = BstSuccessor()
self.assertEqual(bst_successor.get_next(nodes[4]), 5)
self.assertEqual(bst_successor.get_next(nodes[5]), 6)
self.assertEqual(bst_successor.get_next(nodes[8]), 9)
self.assertEqual(bst_successor.get_next(nodes[15]), None)

print('Success: test_bst_successor')

def main():
test = TestBstSuccessor()
test.test_bst_successor()
test.assertRaises(TypeError, test.test_bst_successor_empty)

if __name__ == '__main__':
main()


## Solution Notebook¶

Review the Solution Notebook for a discussion on algorithms and code solutions.