public class Tweet {
    static int[] getRecommendedTweets(int[][] followGraph_edges, int[][] likeGraph_edges,
                                      int targetUser, int minLikeThreshold) {

        Set<Integer> targetUsersFollows = new HashSet<>();
        for (int i[]: followGraph_edges){
            if(i[0]==targetUser) targetUsersFollows.add(i[1]);
        }
        Map<Integer,Integer> recomTweets = new HashMap<>();
        for(int i[]:likeGraph_edges){
            if(targetUsersFollows.contains(i[0])){
                if (recomTweets.containsKey(i[1])){
                    recomTweets.put(i[1],recomTweets.get(i[1])+1);
                }
                else recomTweets.put(i[1],1);
            }
        }
        ArrayList<Integer>ansList = new ArrayList<>();
        for(int tweet: recomTweets.keySet()){
            if(recomTweets.get(tweet)>=minLikeThreshold){
                ansList.add(tweet);
            }
        }

        int[] ans = new int [ansList.size()];
        for(int i=0;i<ansList.size();i++){
            ans[i]=ansList.get(i);
        }

        Arrays.sort(ans);

        return ans;


    }

    public static void main(String[] args) throws Exception {
        int[][] followGraph_edges ={{1,2},{1,3},{1,4},{2,3},{2,4},{1,5},{1,6},{1,7},{2,3},{1,11},{1,20},{2,9}};
        int[][] likeGraph_edges ={{2,17},{3,17},{4,17},{7,17},{6,17},{5,12},{3,12},{4,12},{11,12},{20,13},{9,13}};
        int [] ans = getRecommendedTweets(followGraph_edges,likeGraph_edges,1,3);

        for(int i:ans){
            System.out.println(i);
        }


    }


}

就用hashset 和 hashmap 读就成