zoukankan      html  css  js  c++  java
  • leetcode@ [355] Design Twitter (Object Oriented Programming)

    https://leetcode.com/problems/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.
    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);
    Example
    public class Twitter {
        
        class pair {
            public int userId;
            public int tweetId;
            
            public pair(int userId, int tweetId) {
                this.userId = userId;
                this.tweetId = tweetId;
            }
        }
        
        public ArrayList<pair> tweetList =  null;
        public HashMap<Integer, HashSet<Integer> > followList = null;
    
        /** Initialize your data structure here. */
        public Twitter() {
            tweetList = new ArrayList<pair> ();
            followList = new HashMap<Integer, HashSet<Integer> > ();
        }
        
        /** Compose a new tweet. */
        public void postTweet(int userId, int tweetId) {
                
            pair p = new pair(userId, tweetId);
            tweetList.add(p);
        }
        
        /** 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. */
        public List<Integer> getNewsFeed(int userId) {
            
            List<Integer> rs = new ArrayList<Integer> ();
            if(!followList.containsKey(userId)) {
                followList.put(userId, new HashSet<Integer> ());
            }
            
            HashSet<Integer> network = followList.get(userId);
            
            int size = tweetList.size();
            for(int i=size-1, t=10; i>=0 && t>0; --i) {
                pair p = tweetList.get(i);
                //System.out.println(p.userId);
                if(p.userId == userId || network.contains(p.userId)) {
                    rs.add(p.tweetId);
                    --t;
                }
            }
            
            return rs;
        }
        
        /** Follower follows a followee. If the operation is invalid, it should be a no-op. */
        public void follow(int followerId, int followeeId) {
            if(!followList.containsKey(followerId)) {
                followList.put(followerId, new HashSet<Integer> ());
            } 
            followList.get(followerId).add(followeeId);
        }
        
        /** Follower unfollows a followee. If the operation is invalid, it should be a no-op. */
        public void unfollow(int followerId, int followeeId) {
            if(followList.containsKey(followerId)) {
                followList.get(followerId).remove(followeeId);
            }
        }
    }
    
    /**
     * Your Twitter object will be instantiated and called as such:
     * Twitter obj = new Twitter();
     * obj.postTweet(userId,tweetId);
     * List<Integer> param_2 = obj.getNewsFeed(userId);
     * obj.follow(followerId,followeeId);
     * obj.unfollow(followerId,followeeId);
     */
    View Code
  • 相关阅读:
    apache安装错误error: APR not found解决办法
    (总结)Nginx配置文件nginx.conf中文详解
    多级反向代理下,Java获取请求客户端的真实IP地址多中方法整合
    x-forwarded-for的深度挖掘
    hashcode与字符串
    千万不要误用 java 中的 HashCode 方法
    浅谈Java中的hashcode方法
    MySQL中concat函数
    mysql prepare语句使用
    修改表结构
  • 原文地址:https://www.cnblogs.com/fu11211129/p/5625498.html
Copyright © 2011-2022 走看看