211. Add and Search Word - Data structure design

 1 public class WordDictionary {
 2     private static final int R = 26;
 3     private Node root;
 4     
 5     private static class Node {
 6         private boolean inWord;
 7         private Node[] next = new Node[R];
 8     }
 9     /** Initialize your data structure here. */
10     public WordDictionary() {
11         root = new Node();
12     }
13     
14     /** Adds a word into the data structure. */
15     public void addWord(String word) {
16         if (word == null || word.length() == 0) {
17             return;
18         }
19         Node node = root;
20         int d = 0;
21         while (d < word.length()) {
22             char c = word.charAt(d);
23             if(node.next[c - ‘a‘] == null) {
24                 node.next[c - ‘a‘] = new Node();
25             }
26             node = node.next[c - ‘a‘];
27             d++;
28         }
29         node.inWord = true;
30     }
31     
32     /** Returns if the word is in the data structure. A word could contain the dot character ‘.‘ to represent any one letter. */
33     public boolean search(String word) {
34         if (word == null || word.length() == 0) {
35             return false;
36         }
37         return search(root, word, 0);
38     }
39     private boolean search(Node x, String key, int d) {
40         if (x == null) {
41             return false;
42         }
43         if (d == key.length()) {
44             return x.inWord;
45         }
46         char c = key.charAt(d);
47         if (c == ‘.‘) {
48             for (Node node: x.next) {
49                 if (node != null && search(node, key, d + 1)) {
50                     return true;
51                 }
52             }
53             return false;
54         } else {
55             if (x.next[c - ‘a‘] == null) {
56                 return false;
57             }
58             return search(x.next[c - ‘a‘], key, d + 1);
59         }
60     }
61 }
62 
63 /**
64  * Your WordDictionary object will be instantiated and called as such:
65  * WordDictionary obj = new WordDictionary();
66  * obj.addWord(word);
67  * boolean param_2 = obj.search(word);
68  */