This notebook was prepared by Donne Martin. Source and license info is on GitHub.
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.
class Node(object):
def __init__(self, data):
# TODO: Implement me
pass
class Stack(object):
def __init__(self, top=None):
# TODO: Implement me
pass
def push(self, data):
# TODO: Implement me
pass
def pop(self):
# TODO: Implement me
pass
def peek(self):
# TODO: Implement me
pass
def is_empty(self):
# TODO: Implement me
pass
The following unit test is expected to fail until you solve the challenge.
# %load test_stack.py
import unittest
class TestStack(unittest.TestCase):
# TODO: It would be better if we had unit tests for each
# method in addition to the following end-to-end test
def test_end_to_end(self):
print('Test: Empty stack')
stack = Stack()
self.assertEqual(stack.peek(), None)
self.assertEqual(stack.pop(), None)
print('Test: One element')
top = Node(5)
stack = Stack(top)
self.assertEqual(stack.pop(), 5)
self.assertEqual(stack.peek(), None)
print('Test: More than one element')
stack = Stack()
stack.push(1)
stack.push(2)
stack.push(3)
self.assertEqual(stack.pop(), 3)
self.assertEqual(stack.peek(), 2)
self.assertEqual(stack.pop(), 2)
self.assertEqual(stack.peek(), 1)
self.assertEqual(stack.is_empty(), False)
self.assertEqual(stack.pop(), 1)
self.assertEqual(stack.peek(), None)
self.assertEqual(stack.is_empty(), True)
print('Success: test_end_to_end')
def main():
test = TestStack()
test.test_end_to_end()
if __name__ == '__main__':
main()
Review the Solution Notebook for a discussion on algorithms and code solutions.