Mini Twitter

这道题因为tweet类的问题，push模型比较难以实现，因为需要自己手动对tweet加时间戳排序，操作比较复杂，而pull模型基本上只需要一个时间戳同时对getNewsFeed函数进行for循环排序就行了，其他函数的实现则非常简单

'''
Definition of Tweet:
class Tweet:
    @classmethod
    def create(cls, user_id, tweet_text):
         # This will create a new tweet object,
         # and auto fill id
'''
class MiniTwitter:

    def __init__(self):
        # initialize your data structure here.
        self.friendship = collections.defaultdict(set)
        self.timeLineTable = collections.defaultdict(list)
        self.time = 0

    # @param {int} user_id
    # @param {str} tweet
    # @return {Tweet} a tweet
    def postTweet(self, user_id, tweet_text):
        # Write your code here
        tweet = Tweet.create(user_id, tweet_text)
        self.timeLineTable[user_id].append((self.time, tweet,))
        self.time += 1
        return tweet

    # @param {int} user_id
    # return {Tweet[]} 10 new feeds recently
    # and sort by timeline
    def getNewsFeed(self, user_id):
        # Write your code here
        result = []
        for friend in self.friendship[user_id]:
            if len(self.timeLineTable[friend]) < 10:
                result += self.timeLineTable[friend]
            else:
                result += self.timeLineTable[friend][-10:]
        result += self.timeLineTable[user_id][-10:]
        finalResult = map(lambda x: x[1], sorted(result, reverse=True))
        return finalResult if len(finalResult) < 10 else finalResult[:10]

    # @param {int} user_id
    # return {Tweet[]} 10 new posts recently
    # and sort by timeline
    def getTimeline(self, user_id):
        # Write your code here
        result = map(lambda x: x[1], sorted(self.timeLineTable[user_id], reverse=True))
        return result if len(result) < 10 else result[:10]

    # @param {int} from user_id
    # @param {int} to_user_id
    # from user_id follows to_user_id
    def follow(self, from_user_id, to_user_id):
        # Write your code here
        if from_user_id != to_user_id:
            self.friendship[from_user_id].add(to_user_id)

    # @param {int} from user_id
    # @param {int} to_user_id
    # from user_id unfollows to_user_id
    def unfollow(self, from_user_id, to_user_id):
        # Write your code here
        self.friendship[from_user_id].discard(to_user_id)