Solution.py

class MyQueue:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.s1 = []
        self.s2 = []


    def push(self, x: int) -> None:
        """
        Push element x to the back of queue.
        """
        self.s1.append(x)


    def pop(self) -> int:
        """
        Removes the element from in front of queue and returns that element.
        """
        self._move()
        return self.s2.pop()

    def peek(self) -> int:
        """
        Get the front element.
        """
        self._move()
        return self.s2[-1]


    def empty(self) -> bool:
        """
        Returns whether the queue is empty.
        """
        return len(self.s1) + len(self.s2) == 0
        

    def _move(self):
        """
        Move elements from s1 to s2.
        """
        if len(self.s2) == 0:
            while len(self.s1) > 0:
                self.s2.append(self.s1.pop())


# 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()