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/**
 * Java实现DFA算法进行敏感词过滤
 */
public class SensitiveWordUtil {
    private final TrieNode root;

    public SensitiveWordUtil() {
        root = new TrieNode();
    }

    /**
     * 添加敏感词
     *
     * @param word 词
     */
    public void addWord(String word) {
        TrieNode node = root;
        for (char ch : word.toCharArray()) {
            node = node.getChildren().computeIfAbsent(ch, c -> new TrieNode());
        }
        node.setEndOfWord(true);
    }

    /**
     * 是否在敏感词库中
     *
     * @param word 词
     */
    public boolean containsWord(String word) {
        TrieNode node = root;
        for (char ch : word.toCharArray()) {
            node = node.getChildren().get(ch);
            if (node == null) {
                return false;
            }
        }
        return node.isEndOfWord();
    }

    /**
     * 是否存在敏感词
     *
     * @param text 文本
     */
    public boolean containsSensitiveWord(String text) {
        for (int i = 0; i < text.length(); i++) {
            if (containsWordStartingFromIndex(text, i)) {
                return true;
            }
        }
        return false;
    }

    private boolean containsWordStartingFromIndex(String text, int startIndex) {
        TrieNode node = root;
        for (int i = startIndex; i < text.length(); i++) {
            char ch = text.charAt(i);
            node = node.getChildren().get(ch);
            if (node == null) {
                return false;
            }
            if (node.isEndOfWord()) {
                return true;
            }
        }
        return false;
    }

    /**
     * 将敏感词替换为*
     *
     * @param text 文本
     */
    public String filterWords(String text) {
        StringBuilder filteredText = new StringBuilder();
        StringBuilder word = new StringBuilder();
        TrieNode node = root;

        for (int i = 0; i < text.length(); i++) {
            char ch = text.charAt(i);
            node = node.getChildren().get(ch);

            if (node != null) {
                word.append(ch);
                if (node.isEndOfWord()) {
                    char[] chars = new char[word.length()];
                    Arrays.fill(chars, '*');
                    filteredText.append(new String(chars));
                    word.setLength(0);
                    node = root;
                }
            } else {
                filteredText.append(text.charAt(i));
                node = root;
                word.setLength(0);
            }
        }

        filteredText.append(word);
        return filteredText.toString();
    }

    public List<String> findSensitiveWords(String text) {
        List<String> sensitiveWords = new ArrayList<>();
        for (int i = 0; i < text.length(); i++) {
            int wordEndIndex = findWordEndIndex(text, i);
            if (wordEndIndex != -1) {
                String word = text.substring(i, wordEndIndex + 1);
                if (containsWord(word)) {
                    sensitiveWords.add(word);
                }
                i = wordEndIndex;
            }
        }
        return sensitiveWords;
    }

    private int findWordEndIndex(String text, int startIndex) {
        TrieNode node = root;
        int endIndex = -1;
        for (int i = startIndex; i < text.length(); i++) {
            char ch = text.charAt(i);
            node = node.getChildren().get(ch);
            if (node == null) {
                break;
            }
            if (node.isEndOfWord()) {
                endIndex = i;
            }
        }
        return endIndex;
    }

    private static class TrieNode {
        private final Map<Character, TrieNode> children;
        private boolean endOfWord;

        public TrieNode() {
            children = new HashMap<>();
        }

        public Map<Character, TrieNode> getChildren() {
            return children;
        }

        public boolean isEndOfWord() {
            return endOfWord;
        }

        public void setEndOfWord(boolean endOfWord) {
            this.endOfWord = endOfWord;
        }
    }

    public static void main(String[] args) throws IOException {
        SensitiveWordUtil filter = new SensitiveWordUtil();
        filter.addWord("敏感词1");
        filter.addWord("敏感词2");
        filter.addWord("敏感词3");

        String text = "这是一个包含敏感词1的测试文本，敏感词2也在其中。";

        String filteredText = filter.filterWords(text);
        System.out.println("修正后的内容：" + filteredText);

        List<String> words = filter.findSensitiveWords(text);
        System.out.println("包含以下敏感词：" + words);

        double asDouble = Arrays.stream(new int[10000]).mapToLong(o -> {
            long dfaStartTime = System.nanoTime();
            filter.containsSensitiveWord(text);
            return (System.nanoTime() - dfaStartTime);
        }).average().getAsDouble();
        System.out.println("DFA算法耗时：" + asDouble + "纳秒");

        // 使用正则表达式查找敏感词
        double asDouble1 = Arrays.stream(new int[10000]).mapToLong(o -> {
            long regexStartTime = System.nanoTime();
            boolean regexResult = text.matches(".*(敏感词1|敏感词2|敏感词3).*");
            return (System.nanoTime() - regexStartTime);
        }).average().getAsDouble();
        System.out.println("正则表达式耗时：" + asDouble1 + "纳秒");

        System.out.println(asDouble1 / asDouble);

    }
}