栈和队列

用栈定义队列(出入栈)

class Queue:
    def __init__(self):
        self.pushstack = []
        self.pullstack = []

    def push(self, ob):
        self.pushstack.append(ob)

    def pull(self):
        if self.pullstack:
            return self.pullstack.pop(-1)
        else:
            if not self.pushstack:
                return '&&'
            while self.pushstack:
                self.pullstack.append(self.pushstack.pop(-1))
            return self.pullstack.pop(-1)

用队列定义栈(数据队列和辅助队列)

class Stack:
    def __init__(self):
        self.Data = []
        self.Help = []

    def push(self, ob):
        self.Data.append(ob)

    def swap(self):
        self.Data, self.Help = self.Help, self.Data

    def pop(self):
        while len(self.Data) != 1:
            self.Help.append(self.Data.pop(0))
        self.swap()
        return self.Help.pop(0)