Implement a trie withinsert,search, andstartsWithmethods.

Note:
You may assume that all inputs are consist of lowercase lettersa-z.

tag: Trie

class Trie {

    private class TrieNode{
        TrieNode[] children;
        boolean isWord;

        public TrieNode(){
            children = new TrieNode[26];
            isWord = false;
        }

        public void insert(String word, int index){
            if (index == word.length()){
                this.isWord = true;
                return;
            }

            int pos = word.charAt(index) - 'a';

            if (children[pos] == null){
                children[pos] = new TrieNode();
            }

            children[pos].insert(word, index + 1);
        }

        public TrieNode search(String word, int index){
            if (index == word.length()){
                return this;
            }

            int pos = word.charAt(index) - 'a';

            if (children[pos] == null){
                return null;
            }

            return children[pos].search(word, index + 1);
        }

        public boolean startsWith(String prefix, int index){
            if (index == prefix.length()){
                return true;
            }

            int pos = prefix.charAt(index) - 'a';

            if (children[pos] == null) return false;

            return children[pos].startsWith(prefix, index + 1);
        }
    }

    TrieNode root;

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

    /** Inserts a word into the trie. */
    public void insert(String word) {
        root.insert(word, 0);
    }

    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        TrieNode found = root.search(word, 0);
        return found != null && found.isWord;
    }

    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        return root.startsWith(prefix, 0);
    }
}

/**
 * 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);
 */