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: Check if a binary tree is balanced.

Constraints
Test Cases
Algorithm
Code
Unit Test
Solution Notebook

Constraints

Is a balanced tree one where the heights of two sub trees of any node doesn't differ by more than 1?
- Yes
Can we assume we already have a Node class with an insert method?
- Yes

Test Cases

5, 3, 8, 1, 4 -> Yes
5, 3, 8, 9, 10 -> No

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
%load ../bst/bst.py



In [ ]:

    
def check_balance(root):
    # TODO: Implement me
    pass

Unit Test

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



In [ ]:

    
# %load test_check_balance.py
from nose.tools import assert_equal


class TestCheckBalance(object):

    def test_check_balance(self):
        node = Node(5)
        insert(node, 3)
        insert(node, 8)
        insert(node, 1)
        insert(node, 4)
        assert_equal(check_balance(node), True)

        node = Node(5)
        insert(node, 3)
        insert(node, 8)
        insert(node, 9)
        insert(node, 10)
        assert_equal(check_balance(node), False)

        print('Success: test_check_balance')


def main():
    test = TestCheckBalance()
    test.test_check_balance()


if __name__ == '__main__':
    main()

Solution Notebook

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