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 <= 2) return;
            const int N = board[0].size();
            vector<Point> run; // 没被包含的O，判断后修改为D来标记
            for (int i=0; i<M; ++i)     // 1 边界
                for (int j=0; j<N; ++j) 
                    if ((i==0 || i==M-1 || j==0 || j==N-1) && board[i][j]=='O') { 
                        board[i][j] = 'D';
                        run.push_back(Point(i, j));
                    }

            const static int PATH[4][2] = {{0,1},{0,-1},{-1,0},{1,0}};
            while (!run.empty()) {      // 2 out -> insider
                Point p = run.back();
                run.pop_back();
                for (int i=0; i<4; ++i) {
                    int x = p.x+PATH[i][1];
                    int y = p.y+PATH[i][0];
                    if (x<0 || x>=M || y<0 || y>= N || board[x][y]!='O')
                        continue;
                    board[x][y] = 'D';
                    run.push_back(Point(x, y));
                }
            }

            for (int i=0; i<M; ++i)     // 3 检查
                for (int j=0; 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 < 3)
            return;
  
        for (int j = 0; j < size; ++j) {
            if (board[0][j] == 'O') {
                board[0][j] == '1';
                judgeRegion(board, 1, j);
            }
            
            if (board[size-1][j] == 'O') {
                board[size-1][j] == '1';
                judgeRegion(board, size-2, j);
            }
        }
        
        for (int i = 1; i < size - 1; ++i) {
            if (board[i][0] == 'O') {
                board[i][0] == '1';
                judgeRegion(board, i, 1);
            }
            
            if (board[i][size-1] == 'O') {
                board[i][size-1] == '1';
                judgeRegion(board, i, size - 2);
            }            
        }

        for (int i = 0; i < size; ++i) {
            for (int j = 0; j < size; ++j) {
                if (board[i][j] == 'O')
                    board[i][j] = 'X';
                if (board[i][j] == '1')
                    board[i][j] == 'O';
            }
        }
    }
    
    void judgeRegion(vector<vector<char>> &board, int i, int j) {
        int size = board.size();
        if (i >= 0 && j < size && board[i][j] == 'O') {
            board[i][j] == '1';
            judgeRegion(board, i-1, j);
            judgeRegion(board, i+1, j);
            judgeRegion(board, i, j-1);
            judgeRegion(board, i, j+1);
        }
    }

};