355. 设计推特

/**
* 355. 设计推特
*/
class Twitter {
    /**
    * 保存twitter记录
    */
    private Map<Integer, List<TweetRecord>> tweetMap;
    /**
    * 保存关注关系
    */
    private Map<Integer, Set<Integer>> followMap;
    
    private Long rTime = 0L;
    /** Initialize your data structure here. */
    public Twitter() {
        tweetMap = new HashMap();
        followMap = new HashMap();
    }
    
    /** Compose a new tweet. */
    public void postTweet(int userId, int tweetId) {
        List<TweetRecord> tweetList = tweetMap.get(userId);
        if(tweetList == null){
            tweetList = new ArrayList();
            tweetList.add(new TweetRecord(tweetId, rTime++));
            tweetMap.put(userId, tweetList);
        }else{
            tweetList.add(new TweetRecord(tweetId, rTime++));
        }
    }
    
    /** 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> result = new ArrayList();
        List<TweetRecord> tmpList = new ArrayList();
        if(tweetMap.get(userId) != null){
            tmpList.addAll(tweetMap.get(userId));
        }
        Set<Integer> followIds = followMap.get(userId);
        if(followIds != null) {
        	for(Integer followId: followIds){
                if(followId == userId){
                    continue;
                }
                List<TweetRecord> tweetList = tweetMap.get(followId);
                if(tweetList != null){
                    tmpList.addAll(tweetList);
                }
            }
        }
        Collections.sort(tmpList, new Comparator<TweetRecord>(){
            public int compare(TweetRecord o1, TweetRecord o2){
                return o2.getPubTime().compareTo(o1.getPubTime());
            }
        });
        int count = 0;
        for(TweetRecord tr: tmpList){
            if(count == 10){
                break;
            }
            result.add(tr.getTweetId());
            count++;
        }
        return result;
    }
    
    /** Follower follows a followee. If the operation is invalid, it should be a no-op. */
    public void follow(int followerId, int followeeId) {
        Set<Integer> followList = followMap.get(followerId);
        if(followList == null){
            followList = new HashSet();
            followList.add(followeeId);
            followMap.put(followerId, followList);
        }else{
            followList.add(followeeId);
        }
    }
    
    /** Follower unfollows a followee. If the operation is invalid, it should be a no-op. */
    public void unfollow(int followerId, int followeeId) {
        Set<Integer> followList = followMap.get(followerId);
        if(followList == null){
            return;
        }
        boolean flag = followList.contains(followeeId);
        if(flag){
            followList.remove(followeeId);
        }
    }

    class TweetRecord{
        private Integer tweetId;
        private Long pubTime;

        TweetRecord(Integer id, long time){
            tweetId = id;
            pubTime = time;
        }

        public Long getPubTime(){
            return pubTime;
        }
        public Integer getTweetId(){
            return tweetId;
        }
    }
}

/**
 * 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);
 */