LeetCode—355. Design Twitter

来源：互联网发布：和平崛起知乎编辑：程序博客网时间：2024/04/28 08:06

思路：建立2个List存储Twitter信息（userId和twitterId），建立一个map<Integer,Map<Integer,Integer>>存储follow信息（默认必须存储自己的，当然可以在get的时候添加自己的），剩下的就是一些细节问题，按照题目的意思来。

GitHub地址：https://github.com/corpsepiges/leetcode

点此进入

有Java版本和Python版本，求star。

public class Twitter {    List<Integer> tweetList;    List<Integer> userList;    Map<Integer, Map<Integer,Integer>> followMap;    /** Initialize your data structure here. */    public Twitter() {        tweetList=new ArrayList<Integer>();        userList=new ArrayList<Integer>();        followMap=new HashMap<Integer, Map<Integer,Integer>>();    }        /** Compose a new tweet. */    public void postTweet(int userId, int tweetId) {        if (followMap.get(userId)==null) {            Map<Integer,Integer> map=new HashMap<Integer,Integer>();            map.put(userId, 1);            followMap.put(userId, map);        }        tweetList.add(tweetId);        userList.add(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. */    public List<Integer> getNewsFeed(int userId) {        List<Integer> ans=new ArrayList<Integer>();        if (followMap.get(userId)==null) {            return ans;        }        int i=tweetList.size()-1;        Set<Integer> follow=followMap.get(userId).keySet();        while (i>=0&&ans.size()<10) {            int id=userList.get(i);            int tweet=tweetList.get(i);            if (follow.contains(id)) {                ans.add(tweet);            }            i--;        }        return ans;    }        /** Follower follows a followee. If the operation is invalid, it should be a no-op. */    public void follow(int followerId, int followeeId) {        if (followMap.get(followerId)==null) {            Map<Integer, Integer> map=new HashMap<Integer,Integer>();            map.put(followerId, 1);            followMap.put(followerId, map);        }        followMap.get(followerId).put(followeeId, 1);    }        /** Follower unfollows a followee. If the operation is invalid, it should be a no-op. */    public void unfollow(int followerId, int followeeId) {        if (followerId!=followeeId&&followMap.get(followerId)!=null&&followMap.get(followerId).get(followeeId)!=null) {            followMap.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); */

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