foo.cc: In function 'int main()':
foo.cc:20:3: error: 'memset' was not declared in this scope
   memset(l, 0, 81 * sizeof(int));
   ^~~~~~
foo.cc:20:3: note: suggested alternative: 'wmemset'
   memset(l, 0, 81 * sizeof(int));
   ^~~~~~
   wmemset

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