fish, 80 bytes

Result

AC

Duration

1094ms

Code [DL]

1 ia*i+ad+:*:&-ii*i+&-1-v
!\r'*'o:\/~'*'oaol1=?;&~>48*&r1-:?
: &o:&-1<^!?
&/~&+a

stdin

19
19

stdout

*******************
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*******************

stderr