Implement Trie (Prefix Tree) - Leetcode 208.java

import java.util.HashMap;
import java.util.Map;

class Trie {

    private class TrieNode {
        Map<Character, TrieNode> children = new HashMap<>();
        boolean isEndOfWord = false;
    }

    private TrieNode root;

    /** Initialize your data structure here. */
    public Trie() {
        root = new TrieNode();
    }

    /** Inserts a word into the trie. */
    public void insert(String word) {
        TrieNode node = root;
        for (char c : word.toCharArray()) {
            node.children.putIfAbsent(c, new TrieNode());
            node = node.children.get(c);
        }
        node.isEndOfWord = true;
    }

    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        TrieNode node = root;
        for (char c : word.toCharArray()) {
            if (!node.children.containsKey(c)) {
                return false;
            }
            node = node.children.get(c);
        }
        return node.isEndOfWord;
    }

    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        TrieNode node = root;
        for (char c : prefix.toCharArray()) {
            if (!node.children.containsKey(c)) {
                return false;
            }
            node = node.children.get(c);
        }
        return true;
    }
}