tvl-depot/scratch/data_structures_and_algorithms/reverse-linked-list.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

79 lines
2.2 KiB
Python

import unittest
################################################################################
# Solution
################################################################################
# reverse :: List(a) -> List(a)
def reverse(node):
curr = node
prev = None
while curr:
nxt = curr.next
curr.next = prev
prev = curr
curr = nxt
# Make sure to understand the spec! Debugging takes time. Rewriting takes
# time.
return prev
################################################################################
# Tests
################################################################################
class Test(unittest.TestCase):
class LinkedListNode(object):
def __init__(self, value, next=None):
self.value = value
self.next = next
def get_values(self):
node = self
values = []
while node is not None:
values.append(node.value)
node = node.next
return values
def test_short_linked_list(self):
second = Test.LinkedListNode(2)
first = Test.LinkedListNode(1, second)
result = reverse(first)
self.assertIsNotNone(result)
actual = result.get_values()
expected = [2, 1]
self.assertEqual(actual, expected)
def test_long_linked_list(self):
sixth = Test.LinkedListNode(6)
fifth = Test.LinkedListNode(5, sixth)
fourth = Test.LinkedListNode(4, fifth)
third = Test.LinkedListNode(3, fourth)
second = Test.LinkedListNode(2, third)
first = Test.LinkedListNode(1, second)
result = reverse(first)
self.assertIsNotNone(result)
actual = result.get_values()
expected = [6, 5, 4, 3, 2, 1]
self.assertEqual(actual, expected)
def test_one_element_linked_list(self):
first = Test.LinkedListNode(1)
result = reverse(first)
self.assertIsNotNone(result)
actual = result.get_values()
expected = [1]
self.assertEqual(actual, expected)
def test_empty_linked_list(self):
result = reverse(None)
self.assertIsNone(result)
unittest.main(verbosity=2)