【LeetCode】Surrounded Regions

遍历，遇到O，则push到数组，然后搜寻附近的O，如果遇到边界的O，则表明该区域不是封闭的；如果最后不再找到O，说明该区域封闭，将该区域内元素全改为X。每次处理一个O后都将其改为.，避免重复处理。最后需要将.还原成O。代码如下

class Solution {
public:

    void solve(vector<vector<char>> &board) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        vector<vector<int>> region;

        if(board.size()<2||board[0].size()<2) return;

        for(int i=1;i<board[0].size()-1;i++)
        {
            for(int j=1;j<board.size()-1;j++)
            {
                if(board[j][i]=='O')
                {
                    board[j][i]='.';
                    region.clear();
                    region.push_back(vector<int>(2,j));
                    region[region.size()-1][1]=i;
                    bool flag=true;
                    int oldlen=0;
                    int newlen=region.size();
                    while(oldlen!=newlen)
                    {
                        for(int k=oldlen;k<newlen;k++)
                        {
                            int row=region[k][0],coloum=region[k][1];
                            if(row==0||row==board.size()-1||coloum==0||coloum==board[0].size()-1) {flag=false;};
                            if(row>0&&board[row-1][coloum]=='O')
                                 {region.push_back(vector<int>(2,row-1));region[region.size()-1][1]=coloum;board[row-1][coloum]='.';}
                            if(row<board.size()-1&&board[row+1][coloum]=='O')
                                 {region.push_back(vector<int>(2,row+1));region[region.size()-1][1]=coloum;board[row+1][coloum]='.';}
                            if(coloum>0&&board[row][coloum-1]=='O')
                                 {region.push_back(vector<int>(2,row));region[region.size()-1][1]=coloum-1;board[row][coloum-1]='.';}
                            if(coloum<board[0].size()-1&&board[row][coloum+1]=='O')
                                 {region.push_back(vector<int>(2,row));region[region.size()-1][1]=coloum+1;board[row][coloum+1]='.';}
                        }
                        oldlen=newlen;
                        newlen=region.size();
                    }
                    if(true==flag)
                    {
                        for(int k=0;k<region.size();k++)
                        {
                            int row=region[k][0], coloum=region[k][1];
                            board[row][coloum]='X';
                        }
                    }
                }
            }
        }
        for(int i=0;i<board[0].size();i++)
        {
            for(int j=0;j<board.size();j++)
            {
                if(board[j][i]=='.')
                {
                    board[j][i]='O';
                }
            }
        }
    }
};