class MyQueue():
""" Queue implementation using 2 stacks """
def __init__(self):
self.latest = MyStack()
self.oldest = MyStack()
def __len__(self):
# Data in Queue should always be in one of the two internal stacks
len_latest, len_oldest = len(self.latest), len(self.oldest)
if (len_latest > len_oldest):
return len_latest
return len_oldest
def is_empty(self):
return self.latest.is_empty() and self.oldest.is_empty()
def move(self, from_stack, to_stack):
""" Move top element from from_stack (pop) onto to_stack (push) """
to_stack.push(from_stack.pop())
def push(self, data):
while (self.oldest.is_empty() != True):
self.move(self.oldest, self.latest)
self.latest.push(data)
def pop(self):
while (self.latest.is_empty() != True):
self.move(self.latest, self.oldest)
return self.oldest.pop()
def test_is_empty(self):
stack = MyStack()
self.assertTrue(stack.is_empty())
stack.push(1)
self.assertFalse(stack.is_empty())
stack.pop()
self.assertTrue(stack.is_empty())