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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)
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