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.
%run ../stack/stack.py
%load ../stack/stack.py
import sys
class StackMin(Stack):
def __init__(self, top=None):
# TODO: Implement me
pass
def minimum(self):
# TODO: Implement me
pass
def push(self, data):
# TODO: Implement me
pass
def pop(self):
# TODO: Implement me
pass
The following unit test is expected to fail until you solve the challenge.
# %load test_stack_min.py
import unittest
class TestStackMin(unittest.TestCase):
def test_stack_min(self):
print('Test: Push on empty stack, non-empty stack')
stack = StackMin()
stack.push(5)
self.assertEqual(stack.peek(), 5)
self.assertEqual(stack.minimum(), 5)
stack.push(1)
self.assertEqual(stack.peek(), 1)
self.assertEqual(stack.minimum(), 1)
stack.push(3)
self.assertEqual(stack.peek(), 3)
self.assertEqual(stack.minimum(), 1)
stack.push(0)
self.assertEqual(stack.peek(), 0)
self.assertEqual(stack.minimum(), 0)
print('Test: Pop on non-empty stack')
self.assertEqual(stack.pop(), 0)
self.assertEqual(stack.minimum(), 1)
self.assertEqual(stack.pop(), 3)
self.assertEqual(stack.minimum(), 1)
self.assertEqual(stack.pop(), 1)
self.assertEqual(stack.minimum(), 5)
self.assertEqual(stack.pop(), 5)
self.assertEqual(stack.minimum(), sys.maxsize)
print('Test: Pop empty stack')
self.assertEqual(stack.pop(), None)
print('Success: test_stack_min')
def main():
test = TestStackMin()
test.test_stack_min()
if __name__ == '__main__':
main()
Review the Solution Notebook for a discussion on algorithms and code solutions.