int nk = arr.length - 1 -n; in (nk<n) return; for (int i = n; i <= mk; i++) arr[n][i] = arr[nk][i] = arr [i][n] = arr[i][nk] = n+1; fill (arr, n+1);
int nk = arr.length - 1 -n; in (nk<n) return; for (int i = n; i <= mk; i++) arr[n][i] = arr[nk][i] = arr [i][n] = arr[i][nk] = n+1; fill (arr, n+1);