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

# Challenge Notebook¶

## Constraints¶

• If this is called on a None input or a single node, should we raise an exception?
• Yes
• None -> TypeError
• Single node -> ValueError
• Can we assume we already have a Node class with an insert method?
• Yes
• Can we assume this fits memory?
• Yes

## Test Cases¶

• None or single node -> Exception
Input:
_10_
_/    \_
5        15
/ \       / \
3   8     12  20
/     \         \
2       4        30

Output: 20

Input:
10
/
5
/ \
3   7
Output: 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 Solution(Bst):

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


## Unit Test¶

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

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

class TestBstSecondLargest(unittest.TestCase):

def test_bst_second_largest(self):
bst = Solution(None)
self.assertRaises(TypeError, bst.find_second_largest)
root = Node(10)
bst = Solution(root)
node5 = bst.insert(5)
node15 = bst.insert(15)
node3 = bst.insert(3)
node8 = bst.insert(8)
node12 = bst.insert(12)
node20 = bst.insert(20)
node2 = bst.insert(2)
node4 = bst.insert(4)
node30 = bst.insert(30)
self.assertEqual(bst.find_second_largest(), node20)
root = Node(10)
bst = Solution(root)
node5 = bst.insert(5)
node3 = bst.insert(3)
node7 = bst.insert(7)
self.assertEqual(bst.find_second_largest(), node7)
print('Success: test_bst_second_largest')

def main():
test = TestBstSecondLargest()
test.test_bst_second_largest()

if __name__ == '__main__':
main()


## Solution Notebook¶

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