剑指 Offer 09. 用两个栈实现队列（python）

用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead 操作返回 -1 )

示例：

输入：
["CQueue","appendTail","deleteHead","deleteHead"]
[[],[3],[],[]]
输出：[null,null,3,-1]

class CQueue(object):

    def __init__(self):
        self.stack1 = []
        self.stack2 = []


    def appendTail(self, value):
        """
        :type value: int
        :rtype: None
        """
        self.stack1.append(value)


    def deleteHead(self):
        """
        :rtype: int
        """
        if len(self.stack2) == 0:
            while(self.stack1):
                self.stack2.append(self.stack1.pop())
        if len(self.stack2) == 0:
            return -1
        return self.stack2.pop()
        



# Your CQueue object will be instantiated and called as such:
# obj = CQueue()
# obj.appendTail(value)
# param_2 = obj.deleteHead()