foo.cc: In function 'void fenjiemeiyigeshu(int, int*)':
foo.cc:20:7: warning: statement has no effect [-Wunused-value]
  for(n>0;n/=10;)//这里不知道怎么写这个循环；发现在0后面补一个；就可以了；这是什么原因
      ~^~
foo.cc: In function 'int xunzhaochuxianzuiduodeshu(int*, int, int)':
foo.cc:39:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。