foo.cc: In function 'int main()':
foo.cc:30:16: error: 'sort' was not declared in this scope
   sort(a, a + 9);
                ^
foo.cc:31:28: error: 'unique' was not declared in this scope
   int cnt = unique(a, a + 9) - a;
                            ^

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