class LinkedListQueue:
def __init__(self, capacity=float("inf")):
self._queue = SinglyLinkedList()
self._capacity = capacity
def enqueue(self, data):
if self.get_size() < self._capacity:
self._queue.add_item_end(data)
else:
raise OverflowError()
def dequeue(self):
if self.is_empty():
return None
else:
return self._queue.get_first_item()
def peek(self):
return self._queue.peek_first_item()
def get_size(self):
return self._queue.get_size()
def get_capacity(self):
return self._capacity
def is_empty(self):
return self._queue.is_empty()
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
class Stack(object):
def __init__(self):
self.S = SinglyLinkedList()
def is_empty(self):
return self.S.is_empty()
def push(self, element):
self.S.insert(SinglyLinkedListNode(element)) # Linked list implementation of stack overflow do not exist
def pop(self):
head_node = self.S.delete_head()
if head_node:
return head_node.key
else:
raise IndexError('stack underflow')
class Stack:
def __init__(self, desc=None):
self.__linked_list = SinglyLinkedList()
self.__desc = desc
# self = SinglyLinkedList() does not work. Why???
def push(self, key):
self.__linked_list.push_front(key)
def pop(self):
return self.__linked_list.pop_front()
def top(self):
return self.__linked_list.top_front()
def is_empty(self):
return self.__linked_list.is_empty()
def get_desc(self):
return self.__desc
# cannot use __str__ for the linked_list, b/c it's hidden
def __str__(self):
return str(self.__linked_list) # str(o) calls __str__ method of object o
def test_is_empty(self):
llist = SinglyLinkedList()
self.assertTrue(llist.is_empty())
llist.insert_first(0)
self.assertFalse(llist.is_empty())
def test_empty(self):
linkedlist = SinglyLinkedList()
assert linkedlist.num_nodes == 0
assert list(linkedlist) == []
assert str(linkedlist) == "SinglyLinkedList([])"
assert linkedlist.is_empty()
