Подскажите место с ошибкой в оптимизированном коде

class ReadingManager {
public:
  ReadingManager()
      : user_page_counts_(MAX_USER_COUNT_ + 1, 0),
        sorted_users_(),
        user_positions_(MAX_USER_COUNT_ + 1, -1) {}
 
  void Read(int user_id, int page_count) {
    if (user_page_counts_[user_id] == 0) {
      AddUser(user_id);
    }
    user_page_counts_[user_id] = page_count;
    int& position = user_positions_[user_id];
    while (position > 0 && page_count > user_page_counts_[sorted_users_[position - 1]]) {
      SwapUsers(position, position - 1);
    }
  }
 
  double Cheer(int user_id) const {
    if (user_page_counts_[user_id] == 0) {
      return 0;
    }
    const int user_count = GetUserCount();
    if (user_count == 1) {
      return 1;
    }
    const int page_count = user_page_counts_[user_id];
    int position = user_positions_[user_id];
    while (position < user_count &&
      user_page_counts_[sorted_users_[position]] == page_count) {
      ++position;
    }
    if (position == user_count) {
        return 0;
    }
 
    return (user_count - position) * 1.0 / (user_count - 1);
  }
 
private:
  static const int MAX_USER_COUNT_ = 100000;
 
  vector<int> user_page_counts_;
  vector<int> sorted_users_;
  vector<int> user_positions_;
 
  int GetUserCount() const {
    return sorted_users_.size();
  }
  void AddUser(int user_id) {
    sorted_users_.push_back(user_id);
    user_positions_[user_id] = sorted_users_.size() - 1;
  }
  void SwapUsers(int lhs_position, int rhs_position) {
    const int lhs_id = sorted_users_[lhs_position];
    const int rhs_id = sorted_users_[rhs_position];
    swap(sorted_users_[lhs_position], sorted_users_[rhs_position]);
    swap(user_positions_[lhs_id], user_positions_[rhs_id]);
  }
};

class ReadingManager {
public:
    ReadingManager()
        : user_page_counts_(),
        sorted_users_(),
        user_positions_() {}
 
    void Read(int user_id, int page_count) {
        if (user_page_counts_.count(user_id) != 1) {//Log(Q)
        }
        else {
        int prevP = user_page_counts_[user_id];//Log(Q)
        sorted_users_.erase(user_positions_[user_id]);// amortized O(1)
        }
        user_page_counts_[user_id] = page_count;//Log(Q)
        user_positions_[user_id] = sorted_users_.insert(make_pair(page_count, user_id)); //2Log(Q)
    }
 
    double Cheer(int user_id) {
        if (user_page_counts_.count(user_id) != 1) {//Log(Q)
            return 0;
        }
        multiset<pair<int, int>>::iterator position = user_positions_[user_id]; //Log(Q)
        const int user_count = sorted_users_.size(); // O(1)
        if (user_count == 1) {
            return 1;
        }
        if (position == sorted_users_.begin()) { //Log(N)
            return 0;
        }
        while (position != sorted_users_.begin() 
            && (*position).first == (*prev(position)).first 
            && (*position).second > (*prev(position)).second) {
 
            user_positions_[user_id] = prev(position);
            user_positions_[(*prev(position)).second] = position;
            position = prev(position);
        }
        
        if (position == prev(sorted_users_.end())) { //Log(N)
            return 1;       
        }
        position = next(position);
        const int page_count = user_page_counts_[user_id]; //Log(Q)
        int positionOnRange = distance(sorted_users_.begin(), user_positions_[user_id]) + 1;//Log(Q)
        user_positions_[user_id] = position;
        user_positions_[(*prev(position)).second] = prev(position);
        return 1 - ((user_count - positionOnRange) * 1.0 / (user_count - 1));
    }
 
private:
    map<int, int> user_page_counts_;
    multiset<pair<int, int>> sorted_users_;  
    map<int, multiset<pair<int, int>>::iterator> user_positions_;
};

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  ReadingManager manager;
 
  int query_count;
  cin >> query_count;
 
  for (int query_id = 0; query_id < query_count; ++query_id) {
    string query_type;
    cin >> query_type;
    int user_id;
    cin >> user_id;
 
    if (query_type == "READ") {
      int page_count;
      cin >> page_count;
      manager.Read(user_id, page_count);
    } else if (query_type == "CHEER") {
      cout << setprecision(6) << manager.Cheer(user_id) << "\n";
    }
  }
 
  return 0;
}