C (gcc), (削除) 286 (削除ここまで) (削除) 240 (削除ここまで) 227 bloody bytes (o,_,o)

-46 bloody bytes thanks to ceilingcat!

#define S(x,y)x^=y^=x^=y
o,a,b,c,r;f(int*_){r=0;c=atoi(_);v(o,_,o=strlen(_));r=r;}v(k,_,o,i)char*_;{k-1?({v(k-1,_,o);for(i=0;++i<k;v(k-1,_,o))S(_[k%2?0:i-1],_[k-1]);}):(a=atoi(_)/exp10(o/2))*(b=atoi(_+o/2))==c&&(a+b)%10?r=1:0;}

Try it online!

C (gcc), (削除) 286 (削除ここまで) (削除) 240 (削除ここまで) 218 bloody bytes (o,_,o)

-55 bloody bytes thanks to ceilingcat!

#define S(x,y)x^=y^=x^=y
o,a,b,c,r;f(int*_){c=atoi(_);v(o,_,o=strlen(_),r=0);r=r;}v(k,_,o,i)char*_;{--k?({for(v(k,_,o,0);i<k;v(k,_,o,!++i))S(_[k%2*i],_[k]);}):(a=atoi(_)/exp10(o/2))*(b=atoi(_+o/2))==c&&(a+b)%10?r=1:0;}

Try it online!

C (gcc), (削除) 286 (削除ここまで) (削除) 240 (削除ここまで) 229 bloody bytes (o,_,o)

#define S(x,y)x^=y^=x^=y
o,a,b,c,r;f(_)int*_;{r=0;c=atoi(_);v(o,_,o=strlen(_));r=r;}v(k,_,o,i)char*_;{k-1?({v(k-1,_,o);for(i=0;++i<k;v(k-1,_,o))S(_[k%2?0:i-1],_[k-1]);}):(a=atoi(_)/exp10(o/2))*(b=atoi(_+o/2))==c&&(a+b)%10?r=1:0;}

Try it online!

C (gcc), (削除) 286 (削除ここまで) (削除) 240 (削除ここまで) 227 bloody bytes (o,_,o)

#define S(x,y)x^=y^=x^=y
o,a,b,c,r;f(int*_){r=0;c=atoi(_);v(o,_,o=strlen(_));r=r;}v(k,_,o,i)char*_;{k-1?({v(k-1,_,o);for(i=0;++i<k;v(k-1,_,o))S(_[k%2?0:i-1],_[k-1]);}):(a=atoi(_)/exp10(o/2))*(b=atoi(_+o/2))==c&&(a+b)%10?r=1:0;}

Try it online!

I tried other algorithms, but couldn't find a shorter one. I leave here the dumbest of the tries, which is a solution that doesn't solve the problem. It will probably find most of the vampire numbers though..

I tried other algorithms, but couldn't find a shorter one. I leave here the dumbest of the tries, which is a solution that doesn't solve the problem. It only finds most of the vampire numbers (probably).