chatBot对话挑战，我的代码效率低下？失败的测试用例失败

Question

编辑：这是一个代码挑战。我实际上只是再次运行它，更具体的是代码是无用的。请参阅here和here。

我无法弄清楚我的代码到底出了什么问题。它通过了所有可见的测试用例，但未通过4/5隐藏的测试用例。

面临的挑战是尝试使用之前对话的历史记录（currentConversation）预测给定对话的下一个字词conversations）。如果历史对话的字词与currentConversation匹配，请将其余的历史对话附加到currentConversation。

这是我在Java中的代码：

public String[] chatBot(String[][] conversations, String[] currentConversation) {
    int hmNumOfMatches = 0; // highest matched conversation's similar words to the current conversation
    ArrayList<String> hmRestOfWords = new ArrayList<>(); // the rest of the words in the matched conversation

    // for all given conversations
    for (String[] pc : conversations) {
        int numOfMatches = 0;
        int indexOfLastMatchingWord = -1;
        HashSet<String> uw = new HashSet<String>(); // stores the unique words in pc (possible conversation)

        // for all words of possible conversation
        for (int j = 0; j < pc.length; j++) {
            String pw = pc[j]; // possible word

            // exclude words that have already been accounted for
            if (!uw.contains(pw)) {

                // for all words in the current conversation
                for (int i = 0; i < currentConversation.length; i++) {
                    String w = currentConversation[i];
                    if (w.compareTo(pw) == 0) {
                        numOfMatches++;
                        indexOfLastMatchingWord = j;
                    }
                }
                uw.add(pw);
            }
        }
        ArrayList<String> restOfWords = new ArrayList<>();

        // if there were matching words
        if (indexOfLastMatchingWord != -1)
            restOfWords = getRestOfWords(pc, indexOfLastMatchingWord);
        else continue;

        // set the highest number of matches if it has none
        if (hmNumOfMatches == 0) {
            hmNumOfMatches = numOfMatches;
            hmRestOfWords.addAll(restOfWords);
        }

        // also update it if it's less then the current number of matches
        if (hmNumOfMatches < numOfMatches) {
            hmNumOfMatches = numOfMatches;
            hmRestOfWords = restOfWords;
        }
    }
    /**
     * Create the answer
     */
    String[] answer = new String[currentConversation.length + hmRestOfWords.size()];

    int i;

    // append the current conversation to the answer
    for (i = 0; i < currentConversation.length; i++) {
        answer[i] = currentConversation[i];
    }

    // and append the rest of the words from the matched historical conversation
    for (int j = 0; j < hmRestOfWords.size(); j++) {
        answer[i + j] = hmRestOfWords.get(j);
    }
    return answer;
}

public ArrayList<String> getRestOfWords(String[] pc, int indexOfLastMatchingWord) {
    ArrayList<String> restOfWords = new ArrayList<String>();
    for (int i = indexOfLastMatchingWord + 1; i < pc.length; i++) {
        if (!restOfWords.contains(pc[i])) restOfWords.add(pc[i]);
    }
    return restOfWords;
}