Leetcode Surrounded Regions

题意：将被包围的O改成X。

思路：按边深度搜索。

class Solution {
public:
    int h, w;
    void solve(vector<vector<char>>& board) {
        h = w = 0;
        h = board.size();
        if(h) w = board[0].size();
        for(int i = 0; i < w; i ++) {
            if(board[0][i] == 'O') dfs(board, 0, i);
            if(board[h - 1][i] == 'O') bfs(board, h - 1, i);
        }
        for(int i = 0; i < h; ++ i) {
            if(board[i][0] == 'O') dfs(board, i, 0);
            if(board[i][w - 1] == 'O') bfs(board, i, w - 1);
        }
        
        for(int i = 0; i < h; ++ i) {
            for(int j = 0; j < w; j ++) {
                if(board[i][j] == 'O') board[i][j] = 'X';
                if(board[i][j] == '.') board[i][j] = 'O';
            }
        }
        return;
        
    }
    
        
    void dfs(vector<vector<char>>& myb, int x, int y){
        myb[x][y] = '.';
        if(x + 1 < h && myb[x + 1][y] == 'O') dfs(myb, x + 1, y);
        if(x - 1 > 0 && myb[x - 1][y] == 'O') dfs(myb, x - 1, y);
        if(y + 1 < w && myb[x][y + 1] == 'O') dfs(myb, x, y + 1);
        if(y - 1 > 0 && myb[x][y - 1] == 'O') dfs(myb, x, y - 1);
        return;
    }
};