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authorVincent Ambo <mail@tazj.in>2021-12-13T22·51+0300
committerVincent Ambo <mail@tazj.in>2021-12-13T23·15+0300
commit019f8fd2113df4c5247c3969c60fd4f0e08f91f7 (patch)
tree76a857f61aa88f62a30e854651e8439db77fd0ea /users/wpcarro/scratch/data_structures_and_algorithms/queue-two-stacks.py
parent464bbcb15c09813172c79820bcf526bb10cf4208 (diff)
parent6123e976928ca3d8d93f0b2006b10b5f659eb74d (diff)
subtree(users/wpcarro): docking briefcase at '24f5a642' r/3226
git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c09813172c79820bcf526bb10cf4208
git-subtree-split: 24f5a642af3aa1627bbff977f0a101907a02c69f
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789
Diffstat (limited to 'users/wpcarro/scratch/data_structures_and_algorithms/queue-two-stacks.py')
-rw-r--r--users/wpcarro/scratch/data_structures_and_algorithms/queue-two-stacks.py66
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diff --git a/users/wpcarro/scratch/data_structures_and_algorithms/queue-two-stacks.py b/users/wpcarro/scratch/data_structures_and_algorithms/queue-two-stacks.py
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+++ b/users/wpcarro/scratch/data_structures_and_algorithms/queue-two-stacks.py
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+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)