211 Add and Search Word - Data structure design.js

// 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 letters a-z or .. A . means it can represent any one letter.

// For 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 letters a-z.

// click to show hint.

// Hide Company Tags Facebook
// Hide Tags Backtracking Trie Design
// Hide Similar Problems (M) Implement Trie (Prefix Tree)

function TrieNode(chr) {
    this.val = chr;
    this.isWord = false;
    this.children = [];
}

/**
 * @constructor
 */
var WordDictionary = function() {
   this.root = new TrieNode(null, false);
};

/**
 * @param {string} word
 * @return {void}
 * Adds a word into the data structure.
 */
WordDictionary.prototype.addWord = function(word) {
    var node = this.root;
    for(var i = 0; i < word.length; i++) {
        var chr = word[i];
        node.children[chr] = node.children[chr] || new TrieNode(chr);
        node = node.children[chr];
    }
    
    node.isWord = true;
};

/**
 * @param {string} word
 * @return {boolean}
 * Returns if the word is in the data structure. A word could
 * contain the dot character '.' to represent any one letter.
 */
WordDictionary.prototype.search = function(word) {
    var node = this.root;
    
    function dfs(node, word, i) {
        if(i === word.length) {
            return node.isWord;
        }
        
        var chr = word[i];
        
        if(chr === '.') {
            for(var key in node.children) {
                if(dfs(node.children[key], word, i + 1)) {
                    return true;
                }
            }
        } else if(node.children[chr]) {
            return dfs(node.children[chr], word, i + 1);
        }
        
        return false;
    }
    
    return dfs(node, word, 0);
};

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