CODE

public class Twitter {

  List<int> tweets = new List<int>();
  List<int> postedBy = new List<int>();
  Dictionary<int, List<int>> follows = new Dictionary<int, List<int>>();

  public Twitter() {
    for (int i = 0; i < 10; i ++)
    {
      tweets.Add(-1);
      postedBy.Add(-1);
    }
  }
  
  public void PostTweet(int userId, int tweetId) {
    int i = 0;
    while (i < 10 && tweets[i] > tweetId)
      i++;		
    if (i < 10)
    {
      tweets.Insert(0, tweetId);
      postedBy.Insert(0, userId);
    }
  }
  
  public List<int> GetNewsFeed(int userId) {
    List<int> newsFeed = new List<int>();
    int origUserId = userId;
    int count = 0;
    for (int i = 0; i < tweets.Count; i++)
    {
      if (tweets[i] == -1)
        continue;
      if (count > 9)
        break;

      if (postedBy[i] == userId || (follows.ContainsKey(userId) &&
        follows[userId].Contains(postedBy[i])))
      {
        newsFeed.Add(tweets[i]);
        count++;
      }
      userId = origUserId;
    }
    return newsFeed;
  }
  
  public void Follow(int followerId, int followeeId) {
    if (!follows.ContainsKey(followerId))
    {
      List<int> followees = new List<int>();
      followees.Add(followeeId);
      follows.Add(followerId, followees);
    }
    else if (!follows[followerId].Contains(followeeId))
      follows[followerId].Add(followeeId);
  }
  
  public void Unfollow(int followerId, int followeeId) {
    follows[followerId].Remove(followeeId);        
  }
}