def test_delete(self):
"""
Tests that a Node has been deleted from the
list.
"""
def search_for_val(list, val):
currentNode = list.head
found_val = None
while currentNode.next:
if currentNode.value == val:
found_val = currentNode.value
currentNode = currentNode.next
return found_val
sll = SinglyLinkedList()
sll.add_to_head(1)
sll.add_to_head(2)
sll.add_to_head(3)
sll.add_to_head(4)
sll.add_to_head(5)
node = sll.head
sll.add_to_head(6)
sll.add_to_head(7)
sll.add_to_head(8)
sll.add_to_head(9)
sll.add_to_head(10)
sll.delete(node)
self.assertEqual(search_for_val(sll, node.value), None)
class Stack:
def __init__(self):
self.s = LinkedList()
self.head = self.s.sentinel
def push(self, x):
newnode = Node(x)
self.s.insert(newnode)
def pop(self):
x = self.s.head
if x is None:
raise UnderFlowError
self.s.delete(self.s.head)
return x
def test_delete(self):
""" Test a delete method.
"""
sll = SinglyLinkedList()
node1, node2, node3 = Node(1), Node(2), Node(3)
sll.append(node1)
sll.append(node2)
sll.append(node3)
self.assertEquals(str(sll), '1, 2, 3')
sll.delete(node2)
self.assertEquals(str(sll), '1, 3')
# It silently handles missing items
sll.delete(Node(4))
self.assertEquals(str(sll), '1, 3')
class Queue:
"""
Queue will be implemented with a linked list as the start
of the queue as the tail, and the end of the queue as the head.
This way, enqueue's and dequeue's are O(1).
Enqueue is appending from the tail, dequeueing is reassigning
the pointer of the head to None.
"""
def __init__(self, iterable=None):
self.queue = SinglyLinkedList()
if iterable:
for item in iterable:
self.queue.append(item)
def is_empty(self):
return self.queue.is_empty()
def length(self):
return self.queue.size
def front(self):
if self.queue.is_empty():
return None
return self.queue.head.data
def enqueue(self, data):
self.queue.append(data)
def dequeue(self):
if self.queue.size < 1:
raise ValueError("queue is empty")
output = self.front()
self.queue.delete(output)
return output