力扣-208.实现Trie(前缀树)

题目链接

208.实现Trie(前缀树)

class Trie {
    Trie[] children;
    boolean isEnd;

    public Trie() {
        children = new Trie[26];
        isEnd = false;
    }

    public void insert(String word) {
        Trie node = this;
        int len = word.length();
        for (int i = 0; i < len; i++) {
            int index = word.charAt(i) - 'a';
            if (node.children[index] == null) {
                node.children[index] = new Trie();
            }
            node = node.children[index];
            if (i == len - 1) {
                node.isEnd = true;
            }
        }
    }

    public boolean search(String word) {
        Trie node = this;
        for (int i = 0; i < word.length(); i++) {
            int index = word.charAt(i) - 'a';
            if (node.children[index] == null)
                return false;
            node = node.children[index];
        }
        return node.isEnd;
    }

    public boolean startsWith(String prefix) {
        Trie node = this;
        for (int i = 0; i < prefix.length(); i++) {
            int index = prefix.charAt(i) - 'a';
            if (node.children[index] == null)
                return false;
            node = node.children[index];
        }
        return true;
    }
}

小结：前缀树是一个类似26叉树，并有一个额外标记是否为字符串结尾，插入的时候用一个结点指针依次扫描字符串每一位，不存在则新建。