Leetcode/QueueUsingStack.py at master · vizeit/Leetcode · GitHub

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fromunittestimportTestCase, main

classMyQueue:

def__init__(self):
"""
 Initialize your data structure here.
 """
self._queue= []
self._stack= []

defpush(self, x: int) ->None:
"""
 Push element x to the back of queue.
 """
whilelen(self._queue): self._stack.append(self._queue.pop())
self._queue.append(x)
whilelen(self._stack): self._queue.append(self._stack.pop())

defpop(self) ->int:
"""
 Removes the element from in front of queue and returns that element.
 """
returnself._queue.pop() iflen(self._queue) elseNone

defpeek(self) ->int:
"""
 Get the front element.
 """
returnself._queue[-1] iflen(self._queue) elseNone

defempty(self) ->bool:
"""
 Returns whether the queue is empty.
 """
returnlen(self._queue) ==0


# Your MyQueue object will be instantiated and called as such:
# obj = MyQueue()
# obj.push(x)
# param_2 = obj.pop()
# param_3 = obj.peek()
# param_4 = obj.empty()

classtestQueue(TestCase):
deftest_push(self):
queue=MyQueue()
queue.push(1)
self.assertEqual(queue.peek(), 1)
queue.push(2)
self.assertEqual(queue.peek(), 1)

deftest_pop(self):
queue=MyQueue()
queue.push(1)
self.assertEqual(queue.pop(), 1)
queue.push(2)
self.assertEqual(queue.peek(), 2)

deftest_peek(self):
queue=MyQueue()
queue.push(3)
queue.push(4)
self.assertEqual(queue.peek(),3)

deftest_empty(self):
queue=MyQueue()
self.assertTrue(queue.empty())
queue.push(1)
self.assertFalse(queue.empty())

if__name__=="__main__":
main()