Design a simplified version of a social media service like Twitter where users can post tweets, follow or unfollow other users, and view the $10$ most recent tweets in their news feed.

Implement the Twitter class:

• Twitter() Initializes the Twitter object.

• void postTweet(int userId, int tweetId) Composes a new tweet with ID tweetId published by the user userId. Each call to this function is made with a unique tweetId.

• List[int] getNewsFeed(int userId) Retrieves the $10$ most recent tweet IDs in the user’s news feed. Each item in the news feed must be posted by users whom the user follows or by the user themselves. Tweets must be ordered from most recent to least recent.

• void follow(int followerId, int followeeId) The user with ID followerId starts following the user with ID followeeId.

• void unfollow(int followerId, int followeeId) The user with ID followerId unfollows the user with ID followeeId.

Constraints:

• $1 \leq$ userId, followerId, followeeId $\leq 500$

• $0 \leq$ tweetId $\leq 10^4$

• All the tweets have unique IDs.

• At most $3 \times 10^4$ calls will be made to postTweet, getNewsFeed, follow, and unfollow.

• A user cannot follow himself.

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.