class Stack(object):
def __init__(self):
self.items = LinkedList()
def __str__(self):
s = ', '.join(map(str, self.items))
return 'Stack(>[' + s + '])'
def __len__(self):
return len(self.items)
def isEmpty(self):
return len(self) == 0
def push(self, item):
self.items.appendleft(item)
def pop(self):
try:
return self.items.popleft()
except KeyError:
return None
def peek(self):
return self.items[0]
def clear(self):
while not self.isEmpty():
self.pop()
class Queue(object):
def __init__(self):
self.items = LinkedList()
def __str__(self):
s = ', '.join(map(str, self.items))
return f'Queue([{s}]<)'
def __len__(self):
return len(self.items)
def enqueue(self, item):
"""Items enqueue in the rear(tail) of the list"""
self.items.append(item)
def dequeue(self):
"""Items dequeue from the front(head) of the list"""
return self.items.popleft()
def isEmpty(self):
return len(self) == 0