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de_queue.py
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de_queue.py
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try:
from linked_list.singly_linked_list import SinglyLinkedList
except ImportError:
import sys
import os.path
sys.path.append(os.path.abspath(os.path.join(
os.path.dirname(__file__), os.path.pardir)))
from linked_list.singly_linked_list import SinglyLinkedList
class DEQueue:
''' Double Ended Queue '''
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.__l = SinglyLinkedList()
self.__front = -1
self.__rear = -1
@property
def is_empty(self):
return self.__front == self.__rear
@property
def front(self):
return self.__front
@property
def rear(self):
return self.__rear
def f_enqueue(self, element):
''' Enqueue from front '''
if self.__front == -1:
raise Exception("Cannot insert from front try r_enqueue() instead")
else:
self.__l.unshift(element)
self.__front -= 1
def r_enqueue(self, element):
''' Enqueue from rear '''
self.__l.append(element)
self.__rear += 1
def f_dequeue(self):
''' Dequeue from front '''
if self.is_empty:
return None
self.__front += 1
if self.is_empty:
self.__front, self.__rear = -1, -1
return self.__l.shift()
def r_dequeue(self):
''' Dequeue from rear '''
if self.is_empty:
return None
self.__rear -= 1
if self.is_empty:
self.__front, self.__rear = -1, -1
return self.__l.pop()
def __iter__(self):
for i in self.__l:
yield i
def __str__(self):
return "[" + ", ".join([str(_) for _ in self]) + "]"