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「LeetCode每日一题」—— 355. 设计推特

flypython • • leetcode题解

355. 设计推特

链接：https://leetcode-cn.com/problems/design-twitter/
难度：中等

题目

点击原文链接跳转查看题目

思路

思路见代码。

方案代码

解决方案：

class Twitter:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.user = {}
        self.TweetNum = 0
        self.TweetStack = {}   

    def postTweet(self, userId: int, tweetId: int) -> None:
        """
        Compose a new tweet.
        """
        if not self.user.get(userId, None):
            self.user[userId] = set()        
        self.TweetNum += 1
        if not self.TweetStack.get(userId, None):
            self.TweetStack[userId] = [(tweetId, self.TweetNum)]
        else:
            self.TweetStack[userId].append((tweetId, self.TweetNum))       
        
    def getNewsFeed(self, userId: int) -> List[int]:
        """
        Retrieve the 10 most recent tweet ids in the user's news feed. Each item in the news feed must be posted by users who the user followed or by the user herself. Tweets must be ordered from most recent to least recent.
        """
        if not self.user.get(userId, None):
            self.user[userId] = set()      
        users = self.user[userId] | set([userId]) 
        Tweet_lists = []
        for user in  users:
            if self.TweetStack.get(user, None):
                Tweet_lists += self.TweetStack[user][-10:]
        Tweet_lists.sort(key=lambda x: x[1], reverse=True)
        return [i[0] for i in Tweet_lists[:10]]

    def follow(self, followerId: int, followeeId: int) -> None:
        """
        Follower follows a followee. If the operation is invalid, it should be a no-op.
        """
        if not self.user.get(followeeId, None):
            self.user[followeeId] = set() 
        if followerId == followeeId:
            return None
        if not self.user.get(followerId, None):
            self.user[followerId] = set([followeeId])
        else:
            self.user[followerId].add(followeeId)
        

    def unfollow(self, followerId: int, followeeId: int) -> None:
        """
        Follower unfollows a followee. If the operation is invalid, it should be a no-op.
        """
        if not self.user.get(followerId, None):
            self.user[followerId] = set()
        if not self.user.get(followeeId, None):
            self.user[followeeId] = set() 
        if followerId == followeeId:
            return None
        if followeeId in self.user[followerId]:
            self.user[followerId].remove(followeeId)


# Your Twitter object will be instantiated and called as such:
# obj = Twitter()
# obj.postTweet(userId,tweetId)
# param_2 = obj.getNewsFeed(userId)
# obj.follow(followerId,followeeId)
# obj.unfollow(followerId,followeeId)

原创文章，作者：flypython，如若转载，请注明出处：http://flypython.com/algorithm/leetcode/325.html

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