Surrounded Regions [未完成]

思路完全一样

AC的代码：

 class Solution {
     private:
         struct Point {
             int x, y;
             Point(int _x, int _y):x(_x), y(_y) {}
         };
     public:
         void solve(vector<vector<char> > & board) {
             const int M = board.size();
             if (M <= ) return;
             const int N = board[].size();
             vector<Point> run; // 没被包含的O，判断后修改为D来标记
             for (int i=; i<M; ++i)     // 1 边界
                 for (int j=; j<N; ++j)
                     if ((i== || i==M- || j== || j==N-) && board[i][j]=='O') {
                         board[i][j] = 'D';
                         run.push_back(Point(i, j));
                     }

             const static int PATH[][] = {{,},{,-},{-,},{,}};
             while (!run.empty()) {      // 2 out -> insider
                 Point p = run.back();
                 run.pop_back();
                 for (int i=; i<; ++i) {
                     int x = p.x+PATH[i][];
                     int y = p.y+PATH[i][];
                     if (x< || x>=M || y< || y>= N || board[x][y]!='O')
                         continue;
                     board[x][y] = 'D';
                     run.push_back(Point(x, y));
                 }
             }

             for (int i=; i<M; ++i)     // 3 检查
                 for (int j=; j<N; ++j) {
                     if (board[i][j]=='X') continue;
                     board[i][j] = (board[i][j]=='O'?'X':'O');
                 }
         }
 };

时间通不过的代码：

 class Solution {
 public:
     void solve(vector<vector<char>> &board) {
         int size = board.size();
         if (size < )
             return;

         for (int j = ; j < size; ++j) {
             if (board[][j] == 'O') {
                 board[][j] == '';
                 judgeRegion(board, , j);
             }

             if (board[size-][j] == 'O') {
                 board[size-][j] == '';
                 judgeRegion(board, size-, j);
             }
         }

         for (int i = ; i < size - ; ++i) {
             if (board[i][] == 'O') {
                 board[i][] == '';
                 judgeRegion(board, i, );
             }

             if (board[i][size-] == 'O') {
                 board[i][size-] == '';
                 judgeRegion(board, i, size - );
             }
         }

         for (int i = ; i < size; ++i) {
             for (int j = ; j < size; ++j) {
                 if (board[i][j] == 'O')
                     board[i][j] = 'X';
                 if (board[i][j] == '')
                     board[i][j] == 'O';
             }
         }
     }

     void judgeRegion(vector<vector<char>> &board, int i, int j) {
         int size = board.size();
         if (i >=  && j < size && board[i][j] == 'O') {
             board[i][j] == '';
             judgeRegion(board, i-, j);
             judgeRegion(board, i+, j);
             judgeRegion(board, i, j-);
             judgeRegion(board, i, j+);
         }
     }

 };