Implement Trie (Prefix Tree)

A trie (pronounced as "try") or prefix tree is a tree data structure used to efficiently store and retrieve keys in a dataset of strings. There are various applications of this data structure, such as autocomplete and spellchecker.

Implement the Trie class:

• Trie() Initializes the trie object.
• void insert(String word) Inserts the string word into the trie.
• boolean search(String word) Returns true if the string word is in the trie (i.e., was inserted before), and false otherwise.
• boolean startsWith(String prefix) Returns true if there is a previously inserted string word that has the prefix prefix, and false otherwise.

class Trie {
    class TrieNode {
        public Map<Character, TrieNode> children = new HashMap<>();
        public boolean isWord;
    }
    
    TrieNode root;
    
    public Trie() {
        root = new TrieNode();
    }
    
    public void insert (String word) {
        var node = root;
        for (char c : word.toCharArray()) {
            if (!node.children.containsKey(c)) {
                node.children.put (c, new TrieNode());
            }
            node = node.children.get(c); 
        }
        node.isWord = true;
    }
    
    public boolean search(String word) {
        var node = root;
        for (char c : word.toCharArray()) {
            if (!node.children.containsKey(c)) {
                return false;
            }
            node = node.children.get(c);
        }
        return node.isWord;
    }
    
    public boolean startsWith(String prefix) {
        var node = root;
        for (char c : prefix.toCharArray()) {
            if (!node.children.containsKey(c)) {
                return false;
            }
            node = node.children.get(c);
        }
        return true;
    }
}