Word Search II 460s

 1 public class Solution {
 2     public List<String> findWords(char[][] board, String[] words) {
 3         Trie trie = new Trie();
 4         for (String word : words) {
 5             trie.add(word);
 6         }
 7
 8         List<String> res = new ArrayList<String>();
 9         for (int i = 0; i < board.length; i++) {
10             for (int j = 0; j < board[0].length; j++) {
11                 trie.reset();
12                 search(res, board, "", i, j, trie);
13             }
14         }
15         return res;
16     }
17
18     private void search(List<String> res, char[][] board, String s, int x, int y, Trie trie) {
19         if (x >= board.length || y >= board[0].length || x < 0 || y < 0) {
20             return;
21         }
22         char c = board[x][y];
23         if (c == ‘0‘) {
24             return;
25         }
26         int searchRes = trie.search(c);
27         Node current = trie.getCurrent();
28         s += c;
29         if (searchRes == 0) {
30             return;
31         } else if (searchRes == 1) {
32             current.flag = false;
33             res.add(s);
34         }
35         board[x][y] = ‘0‘;
36         search(res, board, s, x + 1, y, trie);
37         trie.reset(current);
38         search(res, board, s, x - 1, y, trie);
39         trie.reset(current);
40         search(res, board, s, x, y + 1, trie);
41         trie.reset(current);
42         search(res, board, s, x, y - 1, trie);
43         board[x][y] = c;
44     }
45
46     private static class Trie{
47         Node root = new Node();
48         Node current = root;
49
50         public void add(String s) {
51             Node n = root;
52             for (int i = 0; i < s.length(); i++) {
53                 int index = s.charAt(i) - 97;
54                 if (n.nodes[index] == null) {
55                     n.nodes[index] = new Node();
56                 }
57                 n = n.nodes[index];
58             }
59             n.flag = true;
60         }
61
62         public int search(char c) {
63             int index = c - 97;
64             if (current.nodes[index] == null) {
65                 return 0;
66             }
67             current = current.nodes[index];
68             if (current.flag) {
69                 return 1;
70             } else {
71                 return 2;
72             }
73         }
74
75         public Node getCurrent() {
76             return current;
77         }
78
79         public void reset() {
80             current = root;
81         }
82
83         public void reset(Node c) {
84             current = c;
85         }
86     }
87
88     private static class Node{
89         boolean flag;
90         Node[] nodes = new Node[26];
91     }
92 }