'''
CC:

1)Implement Queue Using a linked list
'''
#solution
class Node:
    def __init__(self, data):
       self.data = data
       self.next = None
 
class Queue:
    def __init__(self):
        self.head = None
        self.last = None
 
    def enqueue(self, data):
        if self.last is None:
            self.head = Node(data)
            self.last = self.head
        else:
            self.last.next = Node(data)
            self.last = self.last.next
 
    def dequeue(self):
        if self.head is None:
            return None
        else:
            to_return = self.head.data
            self.head = self.head.next
            return to_return
 
a_queue = Queue()
while True:
    print('enqueue <value>')
    print('dequeue')
    print('quit')
    do = input('What would you like to do? ').split()
 
    operation = do[0].strip().lower()
    if operation == 'enqueue':
        a_queue.enqueue(int(do[1]))
    elif operation == 'dequeue':
        dequeued = a_queue.dequeue()
        if dequeued is None:
            print('Queue is empty.')
        else:
            print('Dequeued element: ', int(dequeued))
    elif operation == 'quit':
        break
'''
2)Implement Stack using a linked list
'''
#solution
class Node:
    def __init__(self, data):
       self.data = data
       self.next = None
 
class Stack:
    def __init__(self):
        self.head = None
 
    def push(self, data):
        if self.head is None:
            self.head = Node(data)
        else:
            new_node = Node(data)
            new_node.next = self.head
            self.head = new_node
 
    def pop(self):
        if self.head is None:
            return None
        else:
            popped = self.head.data
            self.head = self.head.next
            return popped
 
a_stack = Stack()
while True:
    print('push <value>')
    print('pop')
    print('quit')
    do = input('What would you like to do? ').split()
 
    operation = do[0].strip().lower()
    if operation == 'push':
        a_stack.push(int(do[1]))
    elif operation == 'pop':
        popped = a_stack.pop()
        if popped is None:
            print('Stack is empty.')
        else:
            print('Popped value: ', int(popped))
    elif operation == 'quit':
        break