1 public class Solution {
2 public boolean exist(char[][] board, String word) {
3 if(!isValidBoard(board) || word == null || word.length() == 0) {
4 return false;
5 }
6
7 boolean[][] visitedMap = new boolean[board.length][board[0].length];
8 for(int i = 0; i < board.length; i++) {
9 for(int j = 0; j < board[i].length; j++) {
10 if(contains(board, visitedMap, word, i, j, 0)) {
11 return true;
12 }
13 }
14 }
15
16 return false;
17 }
18
19 private boolean isValidBoard(char[][] board) {
20 if(board == null || board.length == 0 || board[0] == null || board[0].length == 0) {
21 return false;
22 } else {
23 return true;
24 }
25 }
26
27 private boolean contains(char[][] board, boolean[][] visitedMap, String word, int i, int j, int index) {
28 if(index >= word.length() || visitedMap[i][j] == true) {
29 return false;
30 } else if(index == word.length()-1 && board[i][j] == word.charAt(index)) {
31 return true;
32 }
33
34 if(board[i][j] == word.charAt(index)) {
35 visitedMap[i][j] = true;
36
37 // upper
38 if(i > 0 && contains(board, visitedMap, word, i-1, j, index+1)) {
39 return true;
40 }
41
42 // down
43 if(i < board.length-1 && contains(board, visitedMap, word, i+1, j, index+1)) {
44 return true;
45 }
46
47 // left
48 if(j > 0 && contains(board, visitedMap, word, i, j-1, index+1)) {
49 return true;
50 }
51
52 // right
53 if(j < board[i].length-1 && contains(board, visitedMap, word, i, j+1, index+1)) {
54 return true;
55 }
56
57 visitedMap[i][j] = false;
58 }
59
60 return false;
61 }
62
63 }
