队列的最大值

请定义一个队列并实现函数 max_value 得到队列里的最大值，要求函数max_value、push_back 和 pop_front 的均摊时间复杂度都是O(1)。

若队列为空，pop_front 和 max_value 需要返回 -1

输入: 
["MaxQueue","push_back","push_back","max_value","pop_front","max_value"]
[[],[1],[2],[],[],[]]
输出: [null,null,null,2,1,2 

class MaxQueue(object):
    '''力扣要求只能导入deque的题解
    可使用queue优化self.que
    '''
    def __init__(self):
        self.que = deque()  # 记录队列值
        self.deque = deque()  # 双向队列按顺序维护最大值

    def max_value(self):
        """
        :rtype: int
        """
        return self.deque[0] if self.deque else -1

    def push_back(self, value):
        """
        :type value: int
        :rtype: None
        """
        self.que.append(value)
        while self.deque and self.deque[-1] < value:
            self.deque.pop()
        self.deque.append(value)

    def pop_front(self):
        """
        :rtype: int
        """
        if not self.que: return -1
        val = self.que.popleft()
        if val == self.deque[0]:
            self.deque.popleft()
        return val


# Your MaxQueue object will be instantiated and called as such:
obj = MaxQueue()
print(obj.max_value())
print(obj.pop_front())
print(obj.pop_front())
obj.push_back(94)
obj.push_back(16)
obj.push_back(89)
print(obj.pop_front())
obj.push_back(22)
print(obj.pop_front())