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import unittest
def kth_to_last_node(k, x):
a, b = x, x
if k == 0:
raise Exception('Value of 0 for k is not supported')
for _ in range(k - 1):
if not a.next:
raise Exception('Value of {} for k is too large'.format(k))
a = a.next
while a.next:
a, b = a.next, b.next
return b
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 setUp(self):
self.fourth = Test.LinkedListNode(4)
self.third = Test.LinkedListNode(3, self.fourth)
self.second = Test.LinkedListNode(2, self.third)
self.first = Test.LinkedListNode(1, self.second)
def test_first_to_last_node(self):
actual = kth_to_last_node(1, self.first)
expected = self.fourth
self.assertEqual(actual, expected)
def test_second_to_last_node(self):
actual = kth_to_last_node(2, self.first)
expected = self.third
self.assertEqual(actual, expected)
def test_first_node(self):
actual = kth_to_last_node(4, self.first)
expected = self.first
self.assertEqual(actual, expected)
def test_k_greater_than_linked_list_length(self):
with self.assertRaises(Exception):
kth_to_last_node(5, self.first)
def test_k_is_zero(self):
with self.assertRaises(Exception):
kth_to_last_node(0, self.first)
unittest.main(verbosity=2)
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