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: Create a linked list for each level of a binary tree.

Constraints
Test Cases
Algorithm
Code
Unit Test
Solution Notebook

Constraints

Is this a binary search tree?
- Yes
Can we assume we already have a Node class with an insert method?
- Yes

Test Cases

5, 3, 8, 2, 4, 1, 7, 6, 9, 10, 11 -> [[5], [3, 8], [2, 4, 7, 9], [1, 6, 10], [11]]

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 create_level_lists(root):
    # TODO: Implement me
    pass

Unit Test

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



In [ ]:

    
%run ../utils/results.py



In [ ]:

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


class TestTreeLevelLists(object):

    def test_tree_level_lists(self):
        node = Node(5)
        insert(node, 3)
        insert(node, 8)
        insert(node, 2)
        insert(node, 4)
        insert(node, 1)
        insert(node, 7)
        insert(node, 6)
        insert(node, 9)
        insert(node, 10)
        insert(node, 11)

        levels = create_level_lists(node)
        results_list = []
        for level in levels:
            results = Results()
            for node in level:
                results.add_result(node)
            results_list.append(results)

        assert_equal(str(results_list[0]), '[5]')
        assert_equal(str(results_list[1]), '[3, 8]')
        assert_equal(str(results_list[2]), '[2, 4, 7, 9]')
        assert_equal(str(results_list[3]), '[1, 6, 10]')
        assert_equal(str(results_list[4]), '[11]')

        print('Success: test_tree_level_lists')


def main():
    test = TestTreeLevelLists()
    test.test_tree_level_lists()


if __name__ == '__main__':
    main()

Solution Notebook

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