class Solution {
public:
vector<vector<int>> move = {{0,1}, {1,0}, {0,-1}, {-1,0}}; //右下左上
vector<vector<bool>> visited;
bool outofArea(vector<vector<char>> board, int y, int x){
return !(x>=0 && y>=0 && y<board.size() && x<board[0].size());
}
bool search(vector<vector<char>>& board, string word, int y, int x){
if (word.length() == 0) return true;
for (int i=0; i<4; i++){
int newx = x + move[i][1];
int newy = y + move[i][0];
if (outofArea(board, newy, newx)) continue;
if (!visited[newy][newx] && board[newy][newx] == word[0]){//匹配成功了且没有用过
visited[newy][newx] = true;
if (search(board, word.substr(1), newy, newx)) return true;
visited[newy][newx] = false;
}
}
return false;
}
bool exist(vector<vector<char>>& board, string word) {
visited = vector<vector<bool>> (board.size(), vector<bool>(board[0].size(), false));
for (int i=0; i<board.size(); i++){//y
for (int j=0; j<board[i].size(); j++){//x
if (board[i][j] == word[0]){
visited[i][j] = true;
if (search(board, word.substr(1), i, j)) return true;
visited[i][j] = false;
}
}
}
return false;
}
};