class Stack:
"""
Stack class implementation
"""
def __init__(self, top=None):
"""
Create a stack by calling this initialization method
Args:
top: Node class default to None. This will be the first element in the stack
"""
# Stack can be implemented with linked-lists as well :D
self.list = LinkedList(top)
def push(self, node):
"""
This operation adds a node into a stack
Args:
node: Node class. The node is added on top of the stack in LIFO manner
Returns:
"""
# This will add an element at the head of the linked-list
self.list.append_left(node)
def pop(self):
"""
This operation will get an element from a stack in LIFO manner
Returns:
Node: top node object within the stack.
"""
# Temporary get the top element
top_element = self.list.head
# Now remove the reference to the next node by calling remove method
self.list.remove(top_element)
# Simply return the top element
return top_element
def peek(self):
"""
You can look up the top element in O(1) time with this method without popping it out
Returns:
int: integer value for the top element in the stack
"""
# Return integer value of the top element
return self.list.head.value
class TestLinkedList(TestCase):
"""
Unit test implementation for LinkedList class
"""
def setUp(self):
"""
Setup method to initialize a linked-list
Returns:
"""
# Create test nodes
self.head_node = Node(1)
self.second_node = Node(2)
self.third_node = Node(3)
# Create test linked-list
self.list = LinkedList(self.head_node)
# Append nodes such that the list is: 1->2->3
self.list.append_right(self.second_node)
self.list.append_right(self.third_node)
def test_append_right(self):
"""
Unit-test for append method in LinkedList class
Returns:
"""
# Append new node with value of 4 such that: 1->2->3->4
current = self.list.head
new_node = Node(4)
self.list.append_right(new_node)
# Check if all values are the same as 1 to 4
for i in range(1, 5):
self.assertEqual(current.value, i)
current = current.next
# Check if the tail element is the new_node
self.assertEqual(new_node.value, self.list.tail.value)
def test_append_left(self):
"""
Unit-test for appending an element as the new head of the
linked-list
Returns:
"""
# Create potential head node
new_node = Node(0)
# Then call the function to set it as the head node
self.list.append_left(new_node)
# Create current node to traverse
current = self.list.head
# Traverse the list, then check the values
for i in range(4):
self.assertEqual(current.value, i)
current = current.next
def test_insert(self):
"""
Unit-test for insert method in LinkedList class
Returns:
"""
# Insert node as the new head: 0->1->2->3
new_node = Node(0)
self.list.insert(new_node, 1)
# Check if correctly inserted or not
self.assertEqual(self.list.head.value, new_node.value)
self.assertEqual(self.list.tail.value, self.third_node.value)
# Insert in the middle of the list: 0->1->5->2->3
new_node = Node(5)
self.list.insert(new_node, 3)
# Check if correctly inserted or not
self.assertEqual(self.list.head.next.next.value, new_node.value)
# Insert node as the tail of the list: 0->1->5->2->3->9
new_node = Node(9)
self.list.insert(new_node, 6)
# Check if correctly inserted or not
self.assertEqual(self.list.tail.value, new_node.value)
# Get temporary access to the list's head
current = self.list.head
# Get the tail node from the list
while current.next:
current = current.next
# Check if correctly inserted or not
self.assertEqual(current.value, new_node.value)
self.assertEqual(current.value, self.list.tail.value)
def test_search(self):
"""
Unit-test for search method in LinkedList class
Returns:
"""
# Check for the head node
head_node = self.list.search(1)
self.assertEqual(head_node, self.head_node)
# Check for the second node
second_node = self.list.search(2)
self.assertEqual(second_node, self.second_node)
# Check for the third node
third_node = self.list.search(3)
self.assertEqual(third_node, self.third_node)
def test_remove(self):
"""
Unit-test for remove method in LinkedList class
Returns:
"""
# Remove the first node in the list: 2->3
self.list.remove(self.head_node)
current = self.list.head
# Check for all nodes which range from 2 to 3
for i in range(2, 4):
self.assertEqual(current.value, i)
current = current.next
# Check is list's head is updated properly
self.assertEqual(self.list.head, self.second_node)
self.assertEqual(self.list.tail, self.third_node)
# Remove the second node in the list: 3
self.list.remove(self.second_node)
self.assertEqual(self.list.head.value, self.third_node.value)
self.assertEqual(self.list.tail, self.third_node)
# Remove the third node in the list, so the head should be None
self.list.remove(self.third_node)
self.assertIsNone(self.list.head)
self.assertIsNone(self.list.tail)
def test_lookup(self):
"""
Unit-test for lookup operation in LinkedList object
Returns:
"""
for i in range(1, 4):
self.assertEqual(self.list.lookup(i), i)
def tearDown(self):
"""
