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: Implement a binary search tree with an insert method.

Constraints
Test Cases
Algorithm
Code
Unit Test

Constraints

Can we assume we are working with valid integers?
- Yes
Can we assume all left descendents <= n < all right descendents?
- Yes
For simplicity, can we use just a Node class without a wrapper Tree class?
- Yes
Do we have to keep track of the parent nodes?
- This is optional

Test Cases

Insert

Insert will be tested through the following traversal:

In-Order Traversal (Provided)

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

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


def insert(root, 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
from nose.tools import assert_equal


class TestTree(object):

    def __init__(self):
        self.results = Results()

    def test_tree(self):
        node = Node(5)
        insert(node, 2)
        insert(node, 8)
        insert(node, 1)
        insert(node, 3)
        in_order_traversal(node, self.results.add_result)
        assert_equal(str(self.results), '[1, 2, 3, 5, 8]')
        self.results.clear_results()

        node = Node(1)
        insert(node, 2)
        insert(node, 3)
        insert(node, 4)
        insert(node, 5)
        in_order_traversal(node, self.results.add_result)
        assert_equal(str(self.results), '[1, 2, 3, 4, 5]')

        print('Success: test_tree')


def main():
    test = TestTree()
    test.test_tree()


if __name__ == '__main__':
    main()

Solution Notebook

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