foo.cc: In function 'int Sort(int*, int)':
foo.cc:30:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
foo.cc: In function 'int main()':
foo.cc:46:18: warning: unused variable 'j' [-Wunused-variable]
  int n,i,x[100], j,y[100]; cin>>n;
                  ^
foo.cc: In function 'int List(int, int*, int)':
foo.cc:41:9: warning: 'go' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return go;
         ^~
foo.cc: In function 'int main()':
foo.cc:46:8: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int n,i,x[100], j,y[100]; cin>>n;
        ^

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