public static int[] getTopKSentence(ArrayList<MySentence> sentences, int k) {
//        ArrayList<MySentence> sentences = MySentence.DatumToSentence(tokens);
        for (MySentence sen_i : sentences) {
            for (MySentence sen_j : sentences) {
                if (sen_j.getScore() > sen_i.getScore()) {
                    sen_i.rank++;       // bao nhiêu câu có score cao hơn sen_i
                }
            }
        }
        int[] topSenIndex = new int[k];
        int counter = 0;
        int rank = 0;
        while (counter < k) {
            for (int i = 0; i < sentences.size(); i++) {
                if (sentences.get(i).rank == rank) {
                    topSenIndex[counter++] = i;
                    if (counter >= k) {
                        break;
                    }
                }
            }
            rank++;
        }
        return topSenIndex;
    }