Design a data structure that supports the following two operations:

void addWord(word)
bool search(word)

search(word) can search a literal word or a regular expression string containing only lettersa-zor.. A.means it can represent any one letter.

Example:

addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true

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

class WordDictionary {

    class Node {
        //public char c;
        public Node[] children;
        public boolean isLeaf;

        public Node() {
            this.children = new Node[26];
        }
    }

    private Node root;

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

    /** Adds a word into the data structure. */
    public void addWord(String word) {
        Node temp = root;
        for(int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);

            if(temp.children[c - 'a'] == null) {
                temp.children[c - 'a'] = new Node();
            }
            temp = temp.children[c - 'a'];
        }
        temp.isLeaf = 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) {
        return search(root, 0, word);
    }

    public boolean search(Node root, int start, String word) {
        if(start == word.length()) {
            return root.isLeaf;
        }

        char c = word.charAt(start);

        if(c == '.') {
            for(int i = 0; i < root.children.length; i++) {
                if(root.children[i] != null) {
                    if(search(root.children[i], start + 1, word))
                        return true;
                }
            }
            return false;
        } else {
            if(root.children[c - 'a'] == null)
                return false;

            return search(root.children[c - 'a'], start + 1, word);
        }

    }
}

/**
 * Your WordDictionary object will be instantiated and called as such:
 * WordDictionary obj = new WordDictionary();
 * obj.addWord(word);
 * boolean param_2 = obj.search(word);
 */