Pila e coda

class Stack:
  def __init__(self):
    self.stack = []
  def push(self, i):
  # i è un elemento da appendere allo stack
    self.stack.append(i)
  def pop(self):
    self.stack.pop()
  def top(self):
    return self.stack[-1]
  def empty(self):
    if self.stack == []:
      return true
    else:
      return false

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class Queue:
  def __init__(self):
    self.queue = []
  def in(self, j):
  #j è l'elemento da appendere alla coda
    self.queue.append(j)
  def out(self):
    self.queue.pop(0)
  def first(self):
    return self.queue[0]
  def last(self):
    return self.queue[-1]
  def empty(self):
    if self.queue == []:
      return true
    else:
      return false