class Queue:
def __init__(self):
self.list = Linked_list()
self.size = 0
def poll(self):
if self.isEmpty():
return None
else:
data = self.peek()
# linked list should store last element and delete node in O(1)
self.list.delete_node(data)
self.size -= 1
return data
def peek(self):
if self.isEmpty():
return None
else:
return self.list.get_head().data
def add(self,data):
self.list.add_node(data)
self.size += 1
def isEmpty(self):
if self.size == 0:
return True
else:
return False
def print_queue(self):
self.list.list_print()
class Stack:
def __init__(self):
self.list = Linked_list()
self.size = 0
def push(self,data):
self.list.add_node_head(data)
self.size += 1
def pop(self):
if self.isEmpty():
return None
else :
data = self.top()
self.list.delete_node(data)
self.size -= 1
return data
def top(self):
if self.isEmpty():
return None
else:
return self.list.get_head().data
def isEmpty(self):
if self.size == 0:
return True
else:
return False