foo.cc: In function 'int main()':
foo.cc:27:11: error: reference to 'max' is ambiguous
   if (g > max.sum) {
           ^~~
foo.cc:15:6: note: candidates are: info max
 info max,i;
      ^~~
In file included from /usr/include/c++/7/bits/char_traits.h:39:0,
                 from /usr/include/c++/7/string:40,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_algobase.h:265:5: note:                 template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/7/bits/stl_algobase.h:219:5: note:                 template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~
foo.cc:28:4: error: reference to 'max' is ambiguous
    max = i;
    ^~~
foo.cc:15:6: note: candidates are: info max
 info max,i;
      ^~~
In file included from /usr/include/c++/7/bits/char_traits.h:39:0,
                 from /usr/include/c++/7/string:40,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_algobase.h:265:5: note:                 template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/7/bits/stl_algobase.h:219:5: note:                 template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~
foo.cc:29:4: error: reference to 'max' is ambiguous
    max.sum = g;
    ^~~
foo.cc:15:6: note: candidates are: info max
 info max,i;
      ^~~
In file included from /usr/include/c++/7/bits/char_traits.h:39:0,
                 from /usr/include/c++/7/string:40,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_algobase.h:265:5: note:                 template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/7/bits/stl_algobase.h:219:5: note:                 template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~
foo.cc:33:10: error: reference to 'max' is ambiguous
  cout << max.s1 << endl << max.sum << endl << s << endl;
          ^~~
foo.cc:15:6: note: candidates are: info max
 info max,i;
      ^~~
In file included from /usr/include/c++/7/bits/char_traits.h:39:0,
                 from /usr/include/c++/7/string:40,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_algobase.h:265:5: note:                 template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/7/bits/stl_algobase.h:219:5: note:                 template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~
foo.cc:33:28: error: reference to 'max' is ambiguous
  cout << max.s1 << endl << max.sum << endl << s << endl;
                            ^~~
foo.cc:15:6: note: candidates are: info max
 info max,i;
      ^~~
In file included from /usr/include/c++/7/bits/char_traits.h:39:0,
                 from /usr/include/c++/7/string:40,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_algobase.h:265:5: note:                 template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/7/bits/stl_algobase.h:219:5: note:                 template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~

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