version at: 2022-04-24

class Trie {
    private final static int N = 26;

    Trie[] childs;
    boolean isEnd;


    public Trie() {
        this.childs = new Trie[N];
        this.isEnd = false;
    }

    public void insert(String word) {
        Trie root = this;
        for (int i = 0; i < word.length(); i++) {
            int index = word.charAt(i) - 'a';

            if (root.childs[index] == null) root.childs[index] = new Trie();

            root = root.childs[index];
        }

        root.isEnd = true;
    }

    public boolean search(String word) {
        Trie node = findPrefixNode(word);

        return node != null && node.isEnd;
    }

    public boolean startsWith(String prefix) {
        return null != findPrefixNode(prefix);
    }


    public Trie findPrefixNode(String word) {
        Trie root = this;

        for (int i = 0; i < word.length(); i++) {
            int index = word.charAt(i) - 'a';

            if (root.childs[index] == null) return null;

            root = root.childs[index];
        }

        return root;
    }
}

/**
 * Your Trie object will be instantiated and called as such:
 * Trie obj = new Trie();
 * obj.insert(word);
 * boolean param_2 = obj.search(word);
 * boolean param_3 = obj.startsWith(prefix);
 */

class Trie {

    static int childNumber = 26;
    boolean isWord;
    Trie[] next;

    /** Initialize your data structure here. */
    public Trie() {
        next = new Trie[childNumber];
        isWord = false;
    }

    /** Inserts a word into the trie. */
    public void insert(String word) { 
        var p = this;
        for (int i = 0; i < word.length(); i++){
            int index = word.charAt(i) - 'a';
            if (p.next[index] == null) p.next[index] = new Trie();
            p = p.next[index];
        }
        p.isWord = true;
    }

    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        var p = this;
        for (int i = 0; i < word.length(); i++){
            int index = word.charAt(i) - 'a';
            if (p.next[index] == null) return false;
            p = p.next[index];
        }
        return p.isWord == true;
    }

    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        var p = this;
        for (int i = 0; i < prefix.length(); i++){
            int index = prefix.charAt(i) - 'a';
            if (p.next[index] == null) return false;
            p = p.next[index];
        }
        return true;
    }
}

/**
 * Your Trie object will be instantiated and called as such:
 * Trie obj = new Trie();
 * obj.insert(word);
 * boolean param_2 = obj.search(word);
 * boolean param_3 = obj.startsWith(prefix);
 */