class Queue(LiuDataStructure):
def __init__(self, iterable=[]):
self.data = LinkedList(iterable)
self.front = None
self.rear = None
self.length = 0
if len(iterable) > 0:
self.front = self.data.get(0)
self.rear = self.data.tail
self.length = self.data.length
def __iter__(self):
while not self.is_empty():
yield self.dequeue()
def __repr__(self):
if self.length > 0:
string = 'Front-> ' + self.data.__repr__() + ' <- Rear'
else:
string = 'Front-> [] <- Rear'
return string
def __getitem__(self, slc_obj):
raise AssertionError("Queue does not support slicing")
def __setitem__(self, slc_obj):
raise AssertionError("Queue does not support slicing")
def enqueue(self, item):
self.data.append(item)
self.length = self.data.length
self.rear = self.data.tail
if self.length == 1:
self.front = item
return self
def dequeue(self):
item = None
try:
item = self.data.remove(0)
self.length = self.data.length
if self.data.length > 0:
self.front = self.data.get(0)
else:
self.front = None
self.rear = None
except IndexError:
raise IndexError('Queue is empty')
return item
def peek(self):
return self.front
def clear(self):
self.front = None
self.rear = None
self.length = 0
self.data = LinkedList()
def is_empty(self):
return self.length == 0
