[LeetCode] Word Search

 1 class Solution {
 2 public:
 3     bool exist(vector<vector<char>>& board, string word) {
 4         int m = board.size(), n = board[0].size();
 5         for (int i = 0; i < m; i++)
 6             for (int j = 0; j < n; j++)
 7                 if (search(board, i, j, word.c_str()))
 8                     return true;
 9         return false;
10     }
11 private:
12     bool search(vector<vector<char>>& board, int r, int c, const char* word) {
13         if (!word[0]) return true;
14         int m = board.size(), n = board[0].size();
15         if (r < 0 || r >= m || c < 0 || c >= n || board[r][c] != word[0]) return false;
16         board[r][c] = ‘$‘;
17         if (search(board, r - 1 ,c, word + 1) || search(board, r + 1, c, word + 1) ||
18             search(board, r, c - 1, word + 1) || search(board, r, c + 1, word + 1))
19             return true;
20         board[r][c] = word[0];
21         return false;
22     }
23 };