操作

• Deque() 创建一个空的双端队列
• add_front(item) 从队头加入一个item元素
• add_rear(item) 从队尾加入一个item元素
• remove_front() 从队头删除一个item元素
• remove_rear() 从队尾删除一个item元素
• is_empty() 判断双端队列是否为空
• size() 返回队列的大小

class Deque(object):    """双端队列"""    def __init__(self):        self.items = []    def is_empty(self):        """判断队列是否为空"""        return self.items == []    def add_front(self, item):        """在队头添加元素"""        self.items.insert(0,item)    def add_rear(self, item):        """在队尾添加元素"""        self.items.append(item)    def remove_front(self):        """从队头删除元素"""        return self.items.pop(0)    def remove_rear(self):        """从队尾删除元素"""        return self.items.pop()    def size(self):        """返回队列大小"""        return len(self.items)if __name__ == "__main__":    deque = Deque()    deque.add_front(1)    deque.add_front(2)    deque.add_rear(3)    deque.add_rear(4)    print deque.size()    print deque.remove_front()    print deque.remove_front()    print deque.remove_rear()    print deque.remove_rear()

 回文检查问题

from pythonds.basic.deque import Dequedef palchecker(aString):    chardeque = Deque()    for ch in aString:        chardeque.addRear(ch)    stillEqual = True    while chardeque.size() > 1 and stillEqual:        first = chardeque.removeFront()        last = chardeque.removeRear()        if first != last:            stillEqual = False    return stillEqualprint(palchecker("lsdkjfskf"))print(palchecker("radar"))