tvl-depot/scratch/data_structures_and_algorithms/queue-two-stacks.py
William Carroll fabf1c9334 Tidy up structure of briefcase
I had a spare fifteen minutes and decided that I should tidy up my
monorepo. The work of tidying up is not finished; this is a small step in the
right direction.

TL;DR
- Created a tools directory
- Created a scratch directory (see README.md for more information)
- Added README.md to third_party
- Renamed delete_dotfile_symlinks -> symlinkManager
- Packaged symlinkManager as an executable symlink-mgr using buildGo
2020-02-12 16:58:29 +00:00

66 lines
1.8 KiB
Python

import unittest
################################################################################
# Solution
################################################################################
class QueueTwoStacks(object):
def __init__(self):
self.a = []
self.b = []
def enqueue(self, x):
self.a.append(x)
def dequeue(self):
if self.b:
return self.b.pop()
else:
while self.a:
self.b.append(self.a.pop())
return self.dequeue()
################################################################################
# Tests
################################################################################
class Test(unittest.TestCase):
def test_basic_queue_operations(self):
queue = QueueTwoStacks()
queue.enqueue(1)
queue.enqueue(2)
queue.enqueue(3)
actual = queue.dequeue()
expected = 1
self.assertEqual(actual, expected)
actual = queue.dequeue()
expected = 2
self.assertEqual(actual, expected)
queue.enqueue(4)
actual = queue.dequeue()
expected = 3
self.assertEqual(actual, expected)
actual = queue.dequeue()
expected = 4
self.assertEqual(actual, expected)
def test_error_when_dequeue_from_new_queue(self):
queue = QueueTwoStacks()
with self.assertRaises(Exception):
queue.dequeue()
def test_error_when_dequeue_from_empty_queue(self):
queue = QueueTwoStacks()
queue.enqueue(1)
queue.enqueue(2)
actual = queue.dequeue()
expected = 1
self.assertEqual(actual, expected)
actual = queue.dequeue()
expected = 2
self.assertEqual(actual, expected)
with self.assertRaises(Exception):
queue.dequeue()
unittest.main(verbosity=2)