tvl-depot/users/wpcarro/scratch/data_structures_and_algorithms/queue-two-stacks.py
Vincent Ambo 019f8fd211 subtree(users/wpcarro): docking briefcase at '24f5a642'
git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c
git-subtree-split: 24f5a642af
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789
2021-12-14 02:15:47 +03:00

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)