def is_palindrome(linked_list):
"""Checks if linked_list is a palindrome.
Creates a second linked list to store the first half of input in reverse
order. Then compares the second half of input with second linked list.
Args:
linked_list: An instance object of tyep LinkedList.
Return:
True if palindrome, false otherwise.
"""
if not linked_list.head or not linked_list.head.next_node:
return True # Consider an empty linked list a palindrome
current = linked_list.head
n = 0
while current:
current = current.next_node
n += 1
k = n // 2
current = linked_list.head
reverse_linked_list = LinkedList()
while k:
reverse_linked_list.insert_at_head(current.data)
current = current.next_node
k -= 1
if n % 2 == 1:
current = current.next_node
p = reverse_linked_list.head
while p:
if p.data != current.data:
return False
p = p.next_node
current = current.next_node
return True
def add_linkedlist_nums(linked_list1, linked_list2):
"""Returns sum of two linked lists representing numbers.
Args:
linked_list1: First number. A LinkedList instance object.
linked_list2: Second number. A LinkedList instance object.
Returns:
Sum as a LinkedList instance object.
"""
sum_linked_list = LinkedList()
current1 = linked_list1.head
current2 = linked_list2.head
current3 = None
carry = 0
while current1 or current2:
subsum = carry
if current1:
subsum += current1.data
current1 = current1.next_node
if current2:
subsum += current2.data
current2 = current2.next_node
carry = subsum // 10
node = Node(subsum % 10)
if not current3:
sum_linked_list.head = node
current3 = node
else:
current3.next_node = node
current3 = node
if carry == 1:
node = Node(1)
current3.next_node = node
return sum_linked_list
def test_find_loop_slow_fast(self):
linked_list = LinkedList()
linked_list.insert_at_head(3)
linked_list.insert_at_head(2)
linked_list.insert_at_head(1)
n1 = linked_list.head
n2 = n1.next_node
n3 = n2.next_node
n3.next_node = n1
self.assertEqual(find_loop_slow_fast(linked_list), 1)
n3.next_node = n2
self.assertEqual(find_loop_slow_fast(linked_list), 2)
n3.next_node = n3
self.assertEqual(find_loop_slow_fast(linked_list), 3)
def test_kth_element_to_last(self):
linked_list = LinkedList()
self.assertEqual(kth_element_to_last(None, 1), None)
self.assertEqual(kth_element_to_last(linked_list, 1), None)
linked_list.insert_at_head(3)
self.assertEqual(kth_element_to_last(linked_list, 0), None)
self.assertEqual(kth_element_to_last(linked_list, 1), 3)
self.assertEqual(kth_element_to_last(linked_list, 2), None)
linked_list.insert_at_head(2)
self.assertEqual(kth_element_to_last(linked_list, 0), None)
self.assertEqual(kth_element_to_last(linked_list, 1), 3)
self.assertEqual(kth_element_to_last(linked_list, 2), 2)
self.assertEqual(kth_element_to_last(linked_list, 3), None)
def test_insert_convert(self):
linked_list = LinkedList()
self.assertEqual(linked_list.convert_to_list(), [])
linked_list.insert_at_head(3)
self.assertEqual(linked_list.convert_to_list(), [3])
linked_list.insert_at_head(2)
self.assertEqual(linked_list.convert_to_list(), [2, 3])
linked_list.insert_at_head(1)
self.assertEqual(linked_list.convert_to_list(), [1, 2, 3])
def test_del_intermediate_node(self):
self.assertFalse(del_intermediate_node(None))
linked_list = LinkedList()
n = linked_list.head
self.assertFalse(del_intermediate_node(n))
linked_list = LinkedList()
linked_list.insert_at_head(3)
self.assertEqual(linked_list.convert_to_list(), [3])
n = linked_list.head
self.assertFalse(del_intermediate_node(n))
self.assertEqual(linked_list.convert_to_list(), [3])
linked_list = LinkedList()
linked_list.insert_at_head(3)
linked_list.insert_at_head(2)
self.assertEqual(linked_list.convert_to_list(), [2, 3])
n = linked_list.head
self.assertTrue(del_intermediate_node(n))
self.assertEqual(linked_list.convert_to_list(), [3])
linked_list = LinkedList()
linked_list.insert_at_head(3)
linked_list.insert_at_head(2)
linked_list.insert_at_head(1)
self.assertEqual(linked_list.convert_to_list(), [1, 2, 3])
n = linked_list.head.next_node.next_node
self.assertFalse(del_intermediate_node(n))
self.assertTrue(linked_list.convert_to_list())
linked_list = LinkedList()
linked_list.insert_at_head(3)
linked_list.insert_at_head(2)
linked_list.insert_at_head(1)
self.assertEqual(linked_list.convert_to_list(), [1, 2, 3])
n = linked_list.head.next_node
self.assertTrue(del_intermediate_node(n))
self.assertEqual(linked_list.convert_to_list(), [1, 3])
linked_list = LinkedList()
linked_list.insert_at_head(3)
linked_list.insert_at_head(2)
linked_list.insert_at_head(1)
self.assertEqual(linked_list.convert_to_list(), [1, 2, 3])
n = linked_list.head
self.assertTrue(del_intermediate_node(n))
self.assertEqual(linked_list.convert_to_list(), [2, 3])
def test_is_palindrome_linkedlist(self):
linked_list = LinkedList()
self.assertTrue(is_palindrome(linked_list))
linked_list.insert_at_head(1)
self.assertTrue(is_palindrome(linked_list))
linked_list.insert_at_head(1)
self.assertTrue(is_palindrome(linked_list))
linked_list.insert_at_head(2)
self.assertFalse(is_palindrome(linked_list))
linked_list.insert_at_head(1)
self.assertFalse(is_palindrome(linked_list))
linked_list.insert_at_head(1)
self.assertTrue(is_palindrome(linked_list))
linked_list.insert_at_head(1)
self.assertFalse(is_palindrome(linked_list))
def test_partition_linkedlist(self):
self.assertIsNone(partition(None, 1))
linked_list = LinkedList()
self.assertEqual(linked_list.convert_to_list(), [])
p_linked_list = partition(linked_list, 1)
self.assertIs(p_linked_list, linked_list)
self.assertEqual(p_linked_list.convert_to_list(), [])
linked_list = LinkedList()
linked_list.insert_at_head(3)
self.assertEqual(linked_list.convert_to_list(), [3])
p_linked_list = partition(linked_list, 1)
self.assertIs(p_linked_list, linked_list)
self.assertEqual(p_linked_list.convert_to_list(), [3])
linked_list = LinkedList()
linked_list.insert_at_head(3)
self.assertEqual(linked_list.convert_to_list(), [3])
p_linked_list = partition(linked_list, 3)
self.assertIs(p_linked_list, linked_list)
self.assertEqual(p_linked_list.convert_to_list(), [3])
linked_list = LinkedList()
linked_list.insert_at_head(3)
self.assertEqual(linked_list.convert_to_list(), [3])
p_linked_list = partition(linked_list, 5)
self.assertIs(p_linked_list, linked_list)
self.assertEqual(p_linked_list.convert_to_list(), [3])
linked_list = LinkedList()
linked_list.insert_at_head(30)
linked_list.insert_at_head(20)
linked_list.insert_at_head(10)
self.assertEqual(linked_list.convert_to_list(), [10, 20, 30])
p_linked_list = partition(linked_list, 10)
self.assertIs(p_linked_list, linked_list)
self.assertEqual(p_linked_list.convert_to_list(), [30, 10, 20])
linked_list = LinkedList()
linked_list.insert_at_head(30)
linked_list.insert_at_head(20)
linked_list.insert_at_head(10)
self.assertEqual(linked_list.convert_to_list(), [10, 20, 30])
p_linked_list = partition(linked_list, 20)
self.assertIs(p_linked_list, linked_list)
self.assertEqual(p_linked_list.convert_to_list(), [10, 30, 20])
linked_list = LinkedList()
linked_list.insert_at_head(30)
linked_list.insert_at_head(20)
linked_list.insert_at_head(10)
self.assertEqual(linked_list.convert_to_list(), [10, 20, 30])
p_linked_list = partition(linked_list, 30)
self.assertIs(p_linked_list, linked_list)
self.assertEqual(p_linked_list.convert_to_list(), [10, 20, 30])
linked_list = LinkedList()
linked_list.insert_at_head(30)
linked_list.insert_at_head(20)
linked_list.insert_at_head(10)
self.assertEqual(linked_list.convert_to_list(), [10, 20, 30])
p_linked_list = partition(linked_list, 40)
self.assertIs(p_linked_list, linked_list)
self.assertEqual(p_linked_list.convert_to_list(), [10, 20, 30])
def test_add_linkedlist_nums(self):
l1 = LinkedList()
l2 = LinkedList()
l3 = add_linkedlist_nums(l1, l2)
self.assertEqual(l3.convert_to_list(), [])
l1 = LinkedList()
l2 = LinkedList()
l1.insert_at_head(1)
l3 = add_linkedlist_nums(l1, l2)
self.assertEqual(l3.convert_to_list(), [1])
l1 = LinkedList()
l2 = LinkedList()
l2.insert_at_head(1)
l3 = add_linkedlist_nums(l1, l2)
self.assertEqual(l3.convert_to_list(), [1])
l1 = LinkedList()
l2 = LinkedList()
l1.insert_at_head(9)
l2.insert_at_head(9)
l3 = add_linkedlist_nums(l1, l2)
self.assertEqual(l3.convert_to_list(), [8, 1])
l1 = LinkedList()
l2 = LinkedList()
l1.insert_at_head(9)
l1.insert_at_head(9)
l2.insert_at_head(1)
l3 = add_linkedlist_nums(l1, l2)
self.assertEqual(l3.convert_to_list(), [0, 0, 1])
def test_remove_duplicates(self):
linked_list = LinkedList()
remove_duplicates(linked_list)
self.assertEqual(linked_list.convert_to_list(), [])
linked_list.insert_at_head(3)
remove_duplicates(linked_list)
self.assertEqual(linked_list.convert_to_list(), [3])
linked_list.insert_at_head(3)
remove_duplicates(linked_list)
self.assertEqual(linked_list.convert_to_list(), [3])
linked_list.insert_at_head(2)
remove_duplicates(linked_list)
self.assertEqual(linked_list.convert_to_list(), [2, 3])
linked_list.insert_at_head(3)
remove_duplicates(linked_list)
self.assertEqual(linked_list.convert_to_list(), [3, 2])
for i in [4, 3, 2, 1]:
linked_list.insert_at_head(i)
remove_duplicates(linked_list)
self.assertEqual(linked_list.convert_to_list(), [1, 2, 3, 4])