g0301_0400.s0355_design_twitter

Class Twitter

java.lang.Object

g0301_0400.s0355_design_twitter.Twitter

public class Twitter
extends Object

355 - Design Twitter.

Medium

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.

Implement the Twitter class:

• Twitter() Initializes your twitter object.
• void postTweet(int userId, int tweetId) Composes a new tweet with ID tweetId by the user userId. Each call to this function will be made with a unique tweetId.
• List<Integer> 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 who the user followed or by the user themself. Tweets must be ordered from most recent to least recent.
• void follow(int followerId, int followeeId) The user with ID followerId started following the user with ID followeeId.
• void unfollow(int followerId, int followeeId) The user with ID followerId started unfollowing the user with ID followeeId.

Example 1:

Input

["Twitter", "postTweet", "getNewsFeed", "follow", "postTweet", "getNewsFeed", "unfollow", "getNewsFeed"]
[[], [1, 5], [1], [1, 2], [2, 6], [1], [1, 2], [1]]

Output:

[null, null, [5], null, null, [6, 5], null, [5]]

Explanation:

Twitter twitter = new Twitter();
twitter.postTweet(1, 5); // User 1 posts a new tweet (id = 5).
twitter.getNewsFeed(1); // User 1's news feed should return a list with 1 tweet id -> [5]. return [5]
twitter.follow(1, 2); // User 1 follows user 2.
twitter.postTweet(2, 6); // User 2 posts a new tweet (id = 6).
twitter.getNewsFeed(1); // 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.unfollow(1, 2); // User 1 unfollows user 2.
twitter.getNewsFeed(1); // User 1's news feed should return a list with 1 tweet id -> [5], since user 1 is no longer following user 2. 

Constraints:

• 1 <= userId, followerId, followeeId <= 500
• 0 <= tweetId <= 104
• All the tweets have unique IDs.
• At most 3 * 104 calls will be made to postTweet, getNewsFeed, follow, and unfollow.

Constructor Summary

Constructors

Constructor and Description
Twitter()

Method Summary

Modifier and Type	Method and Description
void	checkNewUser(int userId)
void	follow(int followerId, int followeeId)
List<Integer>	getNewsFeed(int userId)
void	postTweet(int userId, int tweetId)
void	unfollow(int followerId, int followeeId)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Twitter

public Twitter()

Method Detail

postTweet

public void postTweet(int userId,
                      int tweetId)

getNewsFeed

public List<Integer> getNewsFeed(int userId)

follow

public void follow(int followerId,
                   int followeeId)

unfollow

public void unfollow(int followerId,
                     int followeeId)

checkNewUser

public void checkNewUser(int userId)