079. Word Search

 1 class Solution {
 2 public:
 3     bool exist(vector<vector<char>>& board, string word) {
 4         vector<vector<int>> visited(board.size(), vector<int>(board[0].size(), 0));
 5         for (int i = 0; i < board.size(); ++i) {
 6             for (int j = 0; j < board[0].size(); ++j) {
 7                 if (dfs(board, visited, word, i, j, 0)) return true;
 8             }
 9         }
10         return false;
11     }
12 private:
13     bool dfs(vector<vector<char>>& board, vector<vector<int>>& visited, string word, int x, int y, int pos)
14     {
15         if (!visited[x][y]) {
16             if (board[x][y] == word[pos]) {
17                 visited[x][y] = 1;
18                 if (pos == word.size() - 1) return true;
19                 else {
20                     if (x + 1 < board.size() && !visited[x + 1][y] && dfs(board, visited, word, x + 1, y, pos + 1)) return true;
21                     if (x - 1 >= 0 && !visited[x - 1][y] && dfs(board, visited, word, x - 1, y, pos + 1)) return true;
22                     if (y + 1 < board[0].size() && !visited[x][y + 1] && dfs(board, visited, word, x, y + 1, pos + 1)) return true;
23                     if (y - 1 >= 0 && !visited[x][y - 1] && dfs(board, visited, word, x, y - 1, pos + 1)) return true;
24                 }
25                 visited[x][y] = 0;
26             }
27             else {
28                 return false;
29             }
30         }
31         return false;
32     }
33 };