211. Add and Search Word - Data

public class WordDictionary {
    Trier root=new Trier();
    public void addWord(String word){
        Trier pointer=root;
        for(int i=0;i<word.length();i++){
            char c=word.charAt(i);
            if(pointer.children[c-'a']==null){
                pointer.children[c-'a']=new Trier();
                pointer=pointer.children[c-'a'];
            }else{
                pointer=pointer.children[c-'a'];
            }
        }
        pointer.flag=true;
    }
    

    // Returns if the word is in the data structure. A word could
    // contain the dot character '.' to represent any one letter.
    public boolean search(String word) {
        Trier pointer=root;
        return helper(word,0,pointer);
    }
    private boolean helper(String word,int start,Trier cur){
        if(start==word.length()){
            if(cur.flag) return true;
            else return false;
        }
        char c=word.charAt(start);
        if(c=='.'){
            for(int i=0;i<26;i++){
                if(cur.children[i]!=null)
                    if(helper(word,start+1,cur.children[i])) return true;
            }
        }else{
            if(cur.children[c-'a']==null) return false;
            else return helper(word,start+1,cur.children[c-'a']);
        }
        return false;
    }
    class Trier{
        Trier[] children;
        char c;
        boolean flag;
        public Trier(){
            children=new Trier[26];
            flag=false;
        }
    }
}

// Your WordDictionary object will be instantiated and called as such:
// WordDictionary wordDictionary = new WordDictionary();
// wordDictionary.addWord("word");
// wordDictionary.search("pattern");