[LeetCode] 355. Design Twitter

Design a simplified version of Twitter where users can post tweets, follow/unfollow another user and is able to see the 10 most recent tweets in the user's news feed. Your design should support the following methods:

1. postTweet(userId, tweetId): Compose a new tweet.
2. getNewsFeed(userId): 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.
3. follow(followerId, followeeId): Follower follows a followee.
4. unfollow(followerId, followeeId): Follower unfollows a followee.

Example:

Twitter twitter = new Twitter();

// User 1 posts a new tweet (id = 5).
twitter.postTweet(1, 5);

// User 1's news feed should return a list with 1 tweet id -> [5].
twitter.getNewsFeed(1);

// User 1 follows user 2.
twitter.follow(1, 2);

// User 2 posts a new tweet (id = 6).
twitter.postTweet(2, 6);

// User 1's news feed should return a list with 2 tweet ids -> [6, 5].
// Tweet id 6 should precede tweet id 5 because it is posted after tweet id 5.
twitter.getNewsFeed(1);

// User 1 unfollows user 2.
twitter.unfollow(1, 2);

// User 1's news feed should return a list with 1 tweet id -> [5],
// since user 1 is no longer following user 2.
twitter.getNewsFeed(1);

思路:

細心題

- follow的部分 用一個 字典紀錄 相互關係 所以 follow 和 unfollow 的函數基本上是差不多的
- post 就是一個 list 持續累加
- get  這裡有兩個要求 1) 不能超過 10 個結果 且 要按照時間順序 2) 結果要考慮相互關係




class Twitter(object):

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.userId = None
        self.tweetId = None
        self.followerId = None
        self.followeeId = None
        self.twit = []
        self.followQ = {}

    def postTweet(self, userId, tweetId):
        """
        Compose a new tweet.
        :type userId: int
        :type tweetId: int
        :rtype: void
        """
        self.twit.append((userId, tweetId))
       
    def getNewsFeed(self, userId):
        """
        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.
        :type userId: int
        :rtype: List[int]
        """
        tempRes, count = [], 0
        for i in range(len(self.twit)-1, -1, -1):
            # id is self
            if self.twit[i][0] == userId:
                tempRes.append(self.twit[i][1])
                count += 1
            # id is followee
            elif userId in self.followQ and self.twit[i][0] in self.followQ[userId]:
                tempRes.append(self.twit[i][1])
                count += 1
            # no more than ten
            if count >= 9:
                break
           
        #print self.twit
        return tempRes

    def follow(self, followerId, followeeId):
        """
        Follower follows a followee. If the operation is invalid, it should be a no-op.
        :type followerId: int
        :type followeeId: int
        :rtype: void
        """
        if followerId not in self.followQ:
            self.followQ[followerId] = [followeeId]
        else:
            if followeeId not in self.followQ[followerId]:
                self.followQ[followerId].append(followeeId)

    def unfollow(self, followerId, followeeId):
        """
        Follower unfollows a followee. If the operation is invalid, it should be a no-op.
        :type followerId: int
        :type followeeId: int
        :rtype: void
        """
        if followerId in self.followQ:
            if followeeId in self.followQ[followerId]:
                self.followQ[followerId].remove(followeeId)
               
twitter = Twitter();

# User 1 posts a new tweet (id = 5).
twitter.postTweet(1, 5);

# User 1's news feed should return a list with 1 tweet id -> [5].
twitter.getNewsFeed(1);


# User 1 follows user 2.
twitter.follow(1, 2);

# User 2 posts a new tweet (id = 6).
twitter.postTweet(1, 3);
twitter.postTweet(1, 101);
twitter.postTweet(1, 13);
twitter.postTweet(1, 10);
twitter.postTweet(2, 2);
twitter.postTweet(1, 94);
twitter.postTweet(3, 505);
twitter.postTweet(1, 333);
twitter.postTweet(2, 22);
twitter.postTweet(1, 11);

# User 1's news feed should return a list with 2 tweet ids -> [6, 5].
# Tweet id 6 should precede tweet id 5 because it is posted after tweet id 5.
twitter.getNewsFeed(1);

# User 1 unfollows user 2.
twitter.unfollow(1, 2);

# User 1's news feed should return a list with 1 tweet id -> [5],
# since user 1 is no longer following user 2.
print twitter.getNewsFeed(1);