1+ class WordDictionary {
2+ 3+ class TrieNode {
4+ private TrieNode [] links ;
5+ private boolean end ;
6+ 7+ public TrieNode () {
8+ this .links = new TrieNode [26 ];
9+ }
10+ 11+ public boolean contains (char c ) {
12+ return links [c - 'a' ] != null ;
13+ }
14+ 15+ public void put (char c , TrieNode trieNode ) {
16+ links [c - 'a' ] = trieNode ;
17+ }
18+ 19+ public TrieNode get (char c ) {
20+ return links [c - 'a' ];
21+ }
22+ }
23+ 24+ private TrieNode root ;
25+ 26+ /** Initialize your data structure here. */
27+ public WordDictionary () {
28+ root = new TrieNode ();
29+ }
30+ 31+ /** Adds a word into the data structure. */
32+ public void addWord (String word ) {
33+ TrieNode node = root ;
34+ for (int i = 0 ; i < word .length (); i ++) {
35+ char c = word .charAt (i );
36+ if (!node .contains (c )) {
37+ node .put (c , new TrieNode ());
38+ }
39+ node = node .get (c );
40+ }
41+ node .end = true ;
42+ }
43+ 44+ /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
45+ public boolean search (String word ) {
46+ return searchHelp (word , root );
47+ }
48+ 49+ private boolean searchHelp (String word , TrieNode root ) {
50+ TrieNode node = root ;
51+ for (int i = 0 ; i < word .length (); i ++) {
52+ char c = word .charAt (i );
53+ 54+ if ('.' == c ) {
55+ for (int j = 0 ; j < node .links .length ; j ++) {
56+ if (node .links [j ] != null && searchHelp (word .substring (i + 1 ), node .links [j ])) {
57+ return true ;
58+ }
59+ }
60+ return false ;
61+ }
62+ if (!node .contains (c )) {
63+ return false ;
64+ }
65+ node = node .get (c );
66+ }
67+ return node != null && node .end ;
68+ }
69+ }
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