Leetcode-1031 Number of Enclaves(飞地的数量)

#define _for(i,a,b) for(int i = (a);i < (b);i ++)
#define sz size()
int dx[] = {0,0,1,-1};
int dy[] = {1,-1,0,0};
class Solution
{
    public:
        void floodfill(vector<vector<int>>& A,int i,int j)
        {
            A[i][j] = 0;
            _for(k,0,4) 
            {
                int nx = i+dx[k];
                int ny = j+dy[k];
                if(nx>=0&&ny>=0&&nx<A.size()&&ny<A[nx].size() && A[nx][ny]==1)
                    floodfill(A,nx,ny);
            }
        }
        int numEnclaves(vector<vector<int>>& A)
        {
            _for(i,0,A.sz)
               _for(j,0,A[i].sz)
                    if(A[i][j]==1 && (i==0||i==A.size()-1||j==0||j==A[i].size()-1))
                        floodfill(A,i,j);

            int res = 0;
            _for(i,0,A.sz)
               _for(j,0,A[i].sz)
                    if(A[i][j]==1)
                        res ++;
            return res;
        }
};

flood fill