foo.cc: In function 'int qu(int*, int)':
foo.cc:21:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
foo.cc: In function 'void BubbleSort(int*, int)':
foo.cc:32:6: warning: unused variable 'left' [-Wunused-variable]
  int left,right;
      ^~~~
foo.cc:32:11: warning: unused variable 'right' [-Wunused-variable]
  int left,right;
           ^~~~~

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