[LeetCode]Surrounded Regions

Given a 2D board containing 'X' and 'O', capture all regions surrounded by 'X'.

A region is captured by flipping all 'O's into 'X's in that surrounded region.

For example,

X X X X
X O O X
X X O X
X O X X

After running your function, the board should be:

X X X X
X X X X
X X X X
X O X X

class Solution {
public:
    int dir[4][2] = {{0,1},{0,-1},{1,0},{-1,0}};
    void solveUtil(vector<vector<char> >& board, vector<vector<bool> >& visited, int ix, int iy, vector<pair<int,int> >& curPath, bool& isSurrounded)
    {
        int n = board.size();
        int m = board[0].size();
        queue<pair<int,int> > posQ;
        posQ.push(pair<int,int>(ix, iy));
        while(!posQ.empty())
        {
            int curX = posQ.front().first;
            int curY = posQ.front().second;
            posQ.pop();
            
            if(board[curX][curY] == 'O' && !visited[curX][curY])
            {
                curPath.push_back(pair<int,int>(curX, curY));
                visited[curX][curY] = true;
                for(int k = 0; k < 4; ++k)
                {
                    int newX = curX+dir[k][0];
                    int newY = curY+dir[k][1];
                    if(newX < 0 || newX >= n || newY < 0 || newY >= m) isSurrounded = false;
                    else if (!visited[newX][newY]) posQ.push(pair<int,int>(newX, newY));
                }
                    
            }
        }
        
    }
    void solve(vector<vector<char>> &board) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int n = board.size();
        if(n == 0) return;
        int m = board[0].size();
        
        vector<vector<bool> > visited(n, vector<bool>(m, false));
        for(int i = 0; i < n; ++i)
        {
            for(int j = 0; j < m; ++j)
            {
                vector<pair<int, int> > curPath;
                bool isSurrounded = true;
                if(!visited[i][j]) solveUtil(board, visited, i, j, curPath, isSurrounded);
                if(isSurrounded)    
                {
                    for(int i = 0; i < curPath.size(); ++i) 
                        board[curPath[i].first][curPath[i].second] = 'X';
                }
            }
        }
        
    }
};