两个栈实现队列 Python实现

# coding=utf-8

MAX_LENGTH = 100

SUCCESS = 1
FAIL = 0
ERROR = -1

class Queue(object):

    stack_fir = None
    stack_sec = None
    queue_len = 0

    def __init__(self):
        self.stack_fir = Stack()
        self.stack_sec = Stack()
        self.queue_len = 0

    # 队列push方法
    def push(self, item):
        if self.queue_len == MAX_LENGTH:
            return Result(FAIL, None)
        elif self.queue_len > MAX_LENGTH:
            return Result(ERROR, None)

        self.queue_len += 1
        result = self.stack_fir.push(item)
        if result.get_code() == SUCCESS:
            return Result(SUCCESS, None)
        else:
            return Result(FAIL, None)

    # 队列pop方法
    def pop(self):
        if self.queue_len == 0:
            return Result(FAIL, None)
        elif self.queue_len < 0:
            return Result(ERROR, None)

        self.queue_len -= 1

        # 将装有数据的栈拷贝到空栈中
        while self.stack_fir.has_next():
            pop_result = self.stack_fir.pop()
            if pop_result.get_code() == SUCCESS:
                self.stack_sec.push(pop_result.get_value())

        result = self.stack_sec.pop().get_value()

        # 将装有数据的栈拷贝到空栈中
        while self.stack_sec.has_next():
            pop_result = self.stack_sec.pop()
            if pop_result.get_code() == SUCCESS:
                self.stack_fir.push(pop_result.get_value())

        return Result(SUCCESS, result)

    # 队列是否有下一个元素
    def has_next(self):
        return self.queue_len > 0

class Stack(object):

    stack_len = 0
    item_list = []

    def __init__(self):
        self.stack_len = 0
        self.item_list = []

    # 栈push方法
    def push(self, item):
        if self.stack_len == MAX_LENGTH:
            return Result(FAIL, None)
        elif self.stack_len > MAX_LENGTH:
            return Result(ERROR, None)

        self.stack_len += 1
        self.item_list.append(item)
        return Result(SUCCESS, None)

    # 栈pop方法
    def pop(self):
        if self.stack_len == 0:
            return Result(FAIL, None)
        elif self.stack_len < 0:
            return Result(ERROR, None)

        self.stack_len -= 1
        item = self.item_list[self.stack_len]
        del self.item_list[self.stack_len]
        return Result(SUCCESS, item)

    # 栈是否有下一个元素
    def has_next(self):
        return self.stack_len > 0

class Result(object):
    code = 0
    value = None

    def __init__(self, code, value):
        self.code = code
        self.value = value

    def get_code(self):
        return self.code

    def get_value(self):
        return self.value

if __name__ == '__main__':
    queue = Queue()
    queue.push(1)
    queue.push(2)
    queue.push(5)
    queue.push(4)
    queue.push(3)

    while queue.has_next():
        print queue.pop().get_value()