208. Implement Trie (Prefix Tree)

https://leetcode.com/problems/implement-trie-prefix-tree/

class Trie {
    class Node {
        boolean is_word;
        Map<Character, Node> map;
        Node() {
            map = new HashMap<>();
            is_word = false;
        }
    }
    Node root;
    public Trie() {
        root = new Node();
    }
    
    public void insert(String word) {
        char[] arr = word.toCharArray();
        Node cur = root;
        for (char ch : arr) {
            Node next = cur.map.get(ch);
            if (next == null) {
                next = new Node();
                cur.map.put(ch, next);
            }
            cur = next;
        }
        cur.is_word = true;
    }
    
    public boolean search(String word) {
        char[] arr = word.toCharArray();
        Node cur = root;
        for (char ch : arr) {
            Node next = cur.map.get(ch);
            if (next == null) {
                return false;
            }
            cur = next;
        }
        return cur.is_word;
    }
    
    public boolean startsWith(String prefix) {
        char[] arr = prefix.toCharArray();
        Node cur = root;
        for (char ch : arr) {
            Node next = cur.map.get(ch);
            if (next == null) {
                return false;
            }
            cur = next;
        }
        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);
 */