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

# Challenge Notebook¶

## Constraints¶

• Can the tree have duplicates?
• Yes
• If this is called on a None input, should we raise an exception?
• Yes
• Can we assume we already have a Node class?
• Yes
• Can we assume this fits in memory?
• Yes

## Test Cases¶

Valid:
5
/   \
5     8
/     /
4     6
\
7

Invalid:
5
/   \
5     8
/ \   /
4   9 7


## 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 BstValidate(Bst):

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


## Unit Test¶

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

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

class TestBstValidate(unittest.TestCase):

def test_bst_validate_empty(self):
bst = BstValidate(None)
bst.validate()

def test_bst_validate(self):
bst = BstValidate(Node(5))
bst.insert(8)
bst.insert(5)
bst.insert(6)
bst.insert(4)
bst.insert(7)
self.assertEqual(bst.validate(), True)

bst = BstValidate(Node(5))
left = Node(5)
right = Node(8)
invalid = Node(20)
bst.root.left = left
bst.root.right = right
bst.root.left.right = invalid
self.assertEqual(bst.validate(), False)

print('Success: test_bst_validate')

def main():
test = TestBstValidate()
test.assertRaises(TypeError, test.test_bst_validate_empty)
test.test_bst_validate()

if __name__ == '__main__':
main()


## Solution Notebook¶

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