355. Design Twitter

link

• Use set to record follow status
• Use list to record post
• When get newsfeed, just get every list last record and compare(like merge k list)

class Twitter:

    def __init__(self):
        self.time = 0
        self.P = defaultdict(list)
        self.C = defaultdict(set)

        

    def postTweet(self, userId: int, tweetId: int) -> None:
        self.P[userId].append((self.time,tweetId))
        self.time += 1
        

    def getNewsFeed(self, userId: int) -> List[int]:
        arr = []

        for followeeId in self.C[userId]:
            arr += self.P[followeeId][-10:]

        arr += self.P[userId][-10:]

        return [ t[1] for t in nlargest(10, arr)]
        

    def follow(self, followerId: int, followeeId: int) -> None:
        self.C[followerId].add(followeeId)
        

    def unfollow(self, followerId: int, followeeId: int) -> None:
        if followeeId in self.C[followerId]:
            self.C[followerId].remove(followeeId)