lintcode - 被围绕的区域

 class Solution {
 public:
     /*
      * @param board: board a 2D board containing 'X' and 'O'
      * @return: nothing
      */
     bool flag[][];
     vector<pair<int, int>> v;
     const int dir[][] = {{,}, {,}, {, -}, {-, }};
     int isChange = ;
     void change_board(vector<vector<char>> &board){
         for(size_t i = ; i < v.size(); ++i){
                 int x = v[i].first;
                 int y = v[i].second;
                 board[x][y] = 'X';
         }
     }
     void surroundedRegions(vector<vector<char>> &board) {
         // write your code here
         memset(flag, , sizeof(flag));
         for(size_t i = ; i < board.size(); ++i){
                 for(size_t j = ; j < board[i].size(); ++j){
                         if(flag[i][j] ==  && board[i][j] == 'O'){
                                 v.push_back(make_pair(i,j));
                                 bfs(i,j, board);
                                 if(isChange == ){
                                         //printf("change:%d %d\n",i,j);
                                         change_board(board);
                                 }
                                 v.clear();
                                 isChange = ;
                         }
                 }
         }
     }
     void bfs(int x, int y, vector<vector<char>> board){
         queue<pair<int, int>> que;
         que.push(make_pair(x,y));
         flag[x][y] = ;
         while(!que.empty()){
                 pair<int, int> p = que.front();
                 que.pop();

                 int nx = , ny = ;
                 for(int i = ; i < ; ++i){
                         nx = p.first + dir[i][];
                         ny = p.second + dir[i][];
                         if(nx >=  && nx < board.size() && ny >=  && ny < board[].size()){
                                 if(flag[nx][ny] ==  && board[nx][ny] == 'O'){
                                         v.push_back(make_pair(nx, ny));
                                         que.push(make_pair(nx, ny));
                                         flag[nx][ny] = ;
                                 }
                         } else {
                                // printf("dsad:%d %d\n",nx, ny);
                                 isChange = ;
                         }

                 }
         }
     }
 };

dfs会爆栈 可以 bfs或者用栈模拟函数