foo.cc: In function 'bool check(std::__cxx11::string, std::__cxx11::string)':
foo.cc:15:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<a.size();i++)//逐个比对
              ~^~~~~~~~~

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

{"receive":"2020-07-22T08:02:45.981Z","handle":"2020-07-22T08:02:45.981Z","done":"2020-07-22T08:02:48.697Z"}