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).

Solution Notebook

Problem: Implement breadth-first search on a binary tree.

Constraints
Test Cases
Algorithm
Code
Unit Test

Constraints

Can we assume we already have a Node class with an insert method?
- Yes

Test Cases

Breadth-First Search

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

Algorithm

Initialize queue with root
While queue is not empty
- Dequeue and print the node
- Queue the left child
- Queue the right child

Complexity:

Time: O(n)
Space: O(n)

Code



In [1]:

    
%run ../bst/bst.py



In [2]:

    
from collections import deque


def bfs(root, visit_func):
    queue = deque()
    queue.append(root)
    while queue:
        node = queue.popleft()
        visit_func(node)
        if node.left is not None:
            queue.append(node.left)
        if node.right is not None:
            queue.append(node.right)

Unit Test



In [3]:

    
%run ../utils/results.py



In [4]:

    
%%writefile test_bfs.py
from nose.tools import assert_equal


class TestBfs(object):

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

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

        print('Success: test_bfs')


def main():
    test = TestBfs()
    test.test_bfs()


if __name__ == '__main__':
    main()









    



Overwriting test_bfs.py



In [5]:

    
%run -i test_bfs.py









    



Success: test_bfs