fill recursiv

const int di[]={-1, 0, 1, 0}, dj[]={ 0, 1, 0,-1};
void fill(int i, int j)
{ if(i <= 0 || j <= 0 || i > n || j > m || M[i][j] != 1) return; M[i][j] = 2; for(int k = 0; k < 4; k++) fill(i+di[k], j+dj[k]);
}