import java.util.*;

public class MiniTwitter {

private HashMap<Integer, HashSet<Integer>> followedMap;

private HashMap<Integer, HashSet<Integer>> followMap;

private HashMap<Integer, Stack<Tweet>> msgQ;

public MiniTwitter() {

// initialize your data structure here.

followedMap = new HashMap<Integer,HashSet<Integer>>();

msgQ = new HashMap<Integer, Stack<Tweet>>();

followMap = new HashMap<Integer, HashSet<Integer>>();

}

// @param user_id an integer

// @param tweet a string

// return a tweet

public Tweet postTweet(int user_id, String tweet_text) {

// Write your code here

Tweet t = Tweet.create(user_id, tweet_text);

if(!msgQ.containsKey(user_id)){

msgQ.put(user_id, new Stack<Tweet>());

}

msgQ.get(user_id).add(t);

return t;

}

// @param user_id an integer

// return a list of 10 new feeds recently

// and sort by timeline

public List<Tweet> getNewsFeed(int user_id) {

// Write your code here

ArrayList<Tweet> ret = new ArrayList<Tweet>();

ret.addAll(this.getTimeline(user_id));

if(!followMap.containsKey(user_id))

return ret;

for(Integer follow:followMap.get(user_id)){

ret.addAll(this.getTimeline(follow));

}

Collections.sort(ret, new Comparator<Tweet>() {

@Override

public int compare(Tweet o1, Tweet o2) {

// TODO Auto-generated method stub

return o2.id - o1.id;

}

});

if(ret.size() <= 10)

return ret;

return ret.subList(ret.size()-10, ret.size());

}

// @param user_id an integer

// return a list of 10 new posts recently

// and sort by timeline

public List<Tweet> getTimeline(int user_id) {

ArrayList<Tweet> ret = new ArrayList<Tweet>();

if(!msgQ.containsKey(user_id))

return ret;

for(int i = msgQ.get(user_id).size()-1; i >=0 ; i--){

ret.add(msgQ.get(user_id).get(i));

if(ret.size() == 10)

break;

}

return ret;

}

// @param from_user_id an integer

// @param to_user_id an integer

// from user_id follows to_user_id

public void follow(int from_user_id, int to_user_id) {

// Write your code here

if(!this.followedMap.containsKey(to_user_id))

this.followedMap.put(to_user_id, new HashSet<Integer>());

this.followedMap.get(to_user_id).add(from_user_id);

if(!this.followMap.containsKey(from_user_id))

this.followMap.put(from_user_id, new HashSet<Integer>());

this.followMap.get(from_user_id).add(to_user_id);

}

// @param from_user_id an integer

// @param to_user_id an integer

// from user_id unfollows to_user_id

public void unfollow(int from_user_id, int to_user_id) {

// Write your code here

this.followedMap.get(to_user_id).remove(from_user_id);

this.followMap.get(from_user_id).remove(to_user_id);

}

public static void main(String[] args) {

}

}