# 0211. Design Add and Search Words Data Structure
###### tags: `Leetcode` `Medium` `FaceBook` `Trie`
Link: https://leetcode.com/problems/design-add-and-search-words-data-structure/
## 思路
典型的trie
遇到.就dfs recursive遍历
## Code

class WordDictionary {
    class TrieNode{
        TrieNode[] children = new TrieNode[26];
        boolean isWord = false;
    }
    
    TrieNode root;
    
    public WordDictionary() {
        root = new TrieNode();    
    }
    
    public void addWord(String word) {
        TrieNode curr = root;
        for(int i = 0;i < word.length();i++){
            if(curr.children[word.charAt(i)-'a']==null){
                curr.children[word.charAt(i)-'a'] = new TrieNode();
            }
            curr = curr.children[word.charAt(i)-'a'];
        }
        curr.isWord = true;
    }
    
    public boolean search(String word) {
        TrieNode curr = root;
        return helper(word, curr, 0);
    }
    
    public boolean helper(String word, TrieNode curr, int idx){
        for(int i = idx;i < word.length();i++){
            if(word.charAt(i)!='.'){
                if(curr.children[word.charAt(i)-'a']==null) return false;
                curr = curr.children[word.charAt(i)-'a'];
            }
            else{
                for(char c = 'a';c <= 'z';c++){
                    if(curr.children[c-'a']!=null){
                        if(helper(word, curr.children[c-'a'], i+1)) return true;
                    }
                }
                return false;
            }
        }
        return curr.isWord;
    }
}