class Stack:
def __init__(self):
self.size = 0
self.storage = LinkedList()
def __len__(self):
return self.size
def push(self, value):
self.storage.add_head(value)
self.size += 1 # once you "append", you have to update the count
def pop(self):
if len(self) == 0:
return
self.size -= 1
return self.storage.remove_head()
class Queue:
def __init__(self):
self.size = 0
self.storage = LinkedList()
def __len__(self):
return self.size
def enqueue(self, value):
self.storage.add_head(value)
self.size += 1
def dequeue(self):
if self.size == 0:
return None
else:
self.size -= 1
return self.storage.remove_tail()
