class Stack:
def __init__(self):
self.size = 0
self.storage = LinkedList()
def __len__(self):
return self.size
def push(self, value):
# self.storage.append(value)
self.storage.add_to_end(value)
self.size += 1
def pop(self):
if not self.storage.head:
return None
else:
self.size -= 1
return self.storage.remove_at_end()
