class Solution {
public:
    typedef pair<int, int> pii;
    vector<vector<int>> floodFill(vector<vector<int>>& image, int sr, int sc, int newColor) {
        int n = image.size();
        int m = image[0].size();
        vector<vector<bool>> flag(n, vector<bool>(m, false));
        vector<vector<bool>> vis(n, vector<bool>(m, false));
        queue<pii> qu;
        qu.push({sr, sc});
        vis[sr][sc] = true;
        flag[sr][sc] = true;
        int dx[4] = {-1, 0, 1, 0};
        int dy[4] = {0, -1, 0, 1};
        int cmp = image[sr][sc];
        while(!qu.empty()){
            pii now = qu.front();
            qu.pop();
            for(int i = 0; i < 4; i ++ ){
                int xx = now.first + dx[i];
                int yy = now.second + dy[i];
                if(xx < 0 || xx >= n || yy < 0 || yy >= m)  continue;
                if(vis[xx][yy]) continue;
                if(image[xx][yy] != cmp)    continue;
                qu.push({xx, yy});
                vis[xx][yy] = true;
                flag[xx][yy] = true;
            }
        }
        for(int i = 0; i < n; i ++ ){
            for(int j = 0; j < m; j ++ ){
                if(flag[i][j])  image[i][j] = newColor;
            }
        }
        return image;
    }
};