在Java中实现Trie

我用Java实现了Trie数据结构，但是在运行代码时没有得到正确的答案 . 我用一些简单的字符串构建了trie . 我正在搜索单词和前缀，但结果不合适 . 我已经尝试了很多调试但仍然找不到它可能出错的地方 .

Trie.java：

public class Trie {

    public class Vertex {
        public int words;
        public int prefixes;
        public Vertex edges[] = new Vertex[26];

        public Vertex() {
            this.words = 0;
            this.prefixes = 0;
        }
    }

    private Vertex root;

    Trie() {
        this.root = new Vertex();
    }

    private void addWord(Vertex vertex, String word) {
        if (word.isEmpty()) {
            vertex.words++;
        } else {
            vertex.prefixes++;
            int indexOfNextChar = (int) word.charAt(0) - 97;
            vertex.edges[indexOfNextChar] = new Vertex();
            this.addWord(vertex.edges[indexOfNextChar], word.substring(1));
        }
    }

    private int countWords(Vertex vertex, String word) {
        if (!word.isEmpty()) {
            int indexOfNextChar = (int) word.charAt(0) - 97;
            if (vertex.edges[indexOfNextChar] == null) {
                return 0;
            } else {
                return this.countWords(vertex.edges[indexOfNextChar], word.substring(1));
            }
        } else {
            return vertex.words;
        }
    }

    private int countPrefixes(Vertex vertex, String word) {
        if (!word.isEmpty()) {
            int indexOfNextChar = (int) word.charAt(0) - 97;
            if (vertex.edges[indexOfNextChar] == null) {
                return 0;
            } else {
                return this.countPrefixes(vertex.edges[indexOfNextChar], word.substring(1));
            }
        } else {
            return vertex.prefixes;
        }
    }

    public void addWord(String word) {
        this.addWord(this.root, word.toLowerCase());
    }

    public int countPrefixes(String word) {
        if (word.length() != 0) {
            return this.countPrefixes(this.root, word.toLowerCase());
        }
        return -1;
    }

    public int countWords(String word) {
        if (word.length() != 0) {
            return this.countWords(this.root, word.toLowerCase());
        }
        return -1;
    }
}

TrieTester.java

public class TrieTester {
    public static void main(String[] args) {
        Trie trie = new Trie();
        trie.addWord("Ayush");
        trie.addWord("Ayur");
        trie.addWord("Ayub");
        trie.addWord("Ayan");
        trie.addWord("Bhushan");

        // Should output 0, outputs 0
        System.out.println("Count of word Ayus: " + trie.countWords("Ayus"));

        // Should output 1, outputs 0
        System.out.println("Count of word Ayush: " + trie.countWords("Ayush"));

        // Should output 4, outputs 1
        System.err.println("Count of prefix Ay: " + trie.countPrefixes("Ay"));
    }
}

我提到Topcoder Trie tutorial来实现这一点 .