211. Add and Search Word - Data structure design

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.Example:addWord(“bad”)addWord(“dad”)addWord(“mad”)search(“pad”) -> falsesearch(“bad”) -> truesearch(".ad") -> truesearch(“b..”) -> trueNote:You may assume that all words are consist of lowercase letters a-z.难度：medium题目：设计数据结构支持以下两操作：void addWord(word)bool search(word)search(word) 可以查单词或包含.的正则表达式。 .可以表示任何单个字符。注意：你可以假定所有单词仅由小写字母组成。思路：Tire Tree, DFSRuntime: 94 ms, faster than 89.57% of Java online submissions for Add and Search Word - Data structure design.class WordDictionary { private TrieNode root; /** Initialize your data structure here. / public WordDictionary() { root = new TrieNode(); } /* Adds a word into the data structure. / public void addWord(String word) { char c = word.charAt(0); int i = 0, idx = 0; TrieNode ptr = root; for (; i < word.length(); i++, ptr = ptr.next[idx]) { idx = word.charAt(i) - ‘a’; if (null == ptr.next[idx]) { ptr.next[idx] = new TrieNode(); } } ptr.isWord = true; } // dfs /* 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(word, 0, root); } public boolean search(String word, int idx, TrieNode beginNode) { if (idx >= word.length() || null == beginNode) { return false; } TrieNode node = null; int c = word.charAt(idx), cIdx = c - ‘a’; if (’.’ == c) { boolean result = false; for (int i = 0; i < 26; i++) { node = beginNode.next[i]; if (null == node) { continue; } if ((idx + 1) == word.length() && node.isWord) { return true; } result = result || search(word, idx + 1, beginNode.next[i]); } return result; } // c is not equal to ‘.’ node = beginNode.next[cIdx]; if (null == node) { return false; } if ((idx + 1) == word.length()) { return node.isWord; } return search(word, idx + 1, beginNode.next[cIdx]); } public static class TrieNode { public boolean isWord; public TrieNode[] next = new TrieNode[26]; }}/* * Your WordDictionary object will be instantiated and called as such: * WordDictionary obj = new WordDictionary(); * obj.addWord(word); * boolean param_2 = obj.search(word); */