/in/foo.cc: In function 'std::__cxx11::string zhuanhuan(std::__cxx11::string)':
/in/foo.cc:8:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=0;i<t.length();i++)
          ~^~~~~~~~~~~
/in/foo.cc: In function 'void tj(std::__cxx11::string, int*, int)':
/in/foo.cc:15:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<t.length();i++)
              ~^~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:50:6: warning: unused variable 'i' [-Wunused-variable]
  int i;
      ^