/in/foo.cc: In function 'int main()':
/in/foo.cc:52:6: warning: unused variable 'num' [-Wunused-variable]
  int num=0,pos;
      ^~~
/in/foo.cc:61:32: warning: 'pos' may be used uninitialized in this function [-Wmaybe-uninitialized]
   for(int i=1;i<=tar_set[pos][0];i++){ cout<<tar_set[pos][i]<<' '; }
                  ~~~~~~~~~~~~~~^