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

Challenge Notebook

Problem: Implement a binary search tree with an insert method.

Constraints

  • Can we insert None values?
    • No
  • Can we assume we are working with valid integers?
    • Yes
  • Can we assume all left descendents <= n < all right descendents?
    • Yes
  • Do we have to keep track of the parent nodes?
    • This is optional
  • Can we assume this fits in memory?
    • Yes

Test Cases

Insert

Insert will be tested through the following traversal:

In-Order Traversal

  • 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8
  • 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5

If the root input is None, return a tree with the only element being the new root node.

You do not have to code the in-order traversal, it is part of the unit test.

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 [ ]:
class Node(object):

    def __init__(self, data):
        # TODO: Implement me
        pass


class Bst(object):

    def insert(self, data):
        # TODO: Implement me
        pass

Unit Test

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

In [ ]:
%run dfs.py
In [ ]:
%run ../utils/results.py
In [ ]:
# %load test_bst.py
import unittest


class TestTree(unittest.TestCase):

    def __init__(self, *args, **kwargs):
        super(TestTree, self).__init__()
        self.results = Results()

    def test_tree_one(self):
        bst = Bst()
        bst.insert(5)
        bst.insert(2)
        bst.insert(8)
        bst.insert(1)
        bst.insert(3)
        in_order_traversal(bst.root, self.results.add_result)
        self.assertEqual(str(self.results), '[1, 2, 3, 5, 8]')
        self.results.clear_results()

    def test_tree_two(self):
        bst = Bst()
        bst.insert(1)
        bst.insert(2)
        bst.insert(3)
        bst.insert(4)
        bst.insert(5)
        in_order_traversal(bst.root, self.results.add_result)
        self.assertEqual(str(self.results), '[1, 2, 3, 4, 5]')

        print('Success: test_tree')


def main():
    test = TestTree()
    test.test_tree_one()
    test.test_tree_two()


if __name__ == '__main__':
    main()

Solution Notebook

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