python 栈和队列

"""
栈结构 类似于桶 先进后出   FIFO=first in last out
栈结构的常用方法:
pop 出栈
push 入栈
size 栈大小
isempty 判断栈是否为空
top 获取栈顶元素

"""


class Stack(object):
    def __init__(self):
        self.__stack = []

    def push(self, value):
        self.__stack.append(value)

    def pop(self, value=None):
        if value:
            if value in self.__stack:
                while True:
                    if value == self.__stack.pop():
                        return value
            else:
                raise ValueError("数值不存在，不能出栈")
        else:
            if not self.isempty():
                return self.__stack.pop()
            else:
                raise ValueError("数值不存在，不能删")

    def size(self):
        return len(self.__stack)

    def isempty(self):
        return self.size() == 0
        # return True if len(self.__stack) == 0 else False

    def top(self):
        return self.pop()


stack = Stack()
stack.isempty()
stack.push('a')
stack.push('b')
stack.push('c')
stack.push('d')
print(stack.pop('c'))
print(stack.size())


"""
队列结构 类似于 管道，先进先出， FIFO=first in first out
队列的常用方法
出队
入队
队列长度
队列是否为空
"""


class Queue(object):
    def __init__(self):
        self.__queue = []

    def isempty(self):
        return self.__queue == []

    def size(self):
        return len(self.__queue)

    def enqueue(self, value):
        # 入队
        self.__queue.insert(0, value)
        # self.__queue.append(value)
    # insert(0, value)与pop()对应     append(value)与pop(0)对应

    def dequeue(self):
        # 出队
        self.__queue.pop()
        # self.__queue.pop(0)


q = Queue()
q.enqueue('a')
q.enqueue('b')
q.enqueue('c')
q.enqueue('d')
print(q.size())
print(q.dequeue())



# 双端队列
class Queue(object):
    def __init__(self):
        self.__queue = []

    def isempty(self):
        return len(self.__queue) == 0

    def size(self):
        return len(self.__queue)

    def l_enqueue(self, value):
        self.__queue.insert(0, value)

    def r_dequeue(self):
        return self.__queue.pop()

    def r_enqueue(self, value):
        self.__queue.append(value)

    def l_dequeue(self):
        return self.__queue.pop(0)


q = Queue()
q.l_enqueue('a')
q.l_enqueue('b')
q.r_enqueue('c')
q.r_enqueue('d')
# bacd
print(q.size())
print(q.r_dequeue())
print(q.r_dequeue())
print(q.l_dequeue())
print(q.l_dequeue())
# 出栈顺序：dcba