foo.cc: In function 'int main()':
foo.cc:8:10: warning: unused variable 'm' [-Wunused-variable]
    int n,m,cnt=0;
          ^
foo.cc:8:12: warning: unused variable 'cnt' [-Wunused-variable]
    int n,m,cnt=0;
            ^~~
foo.cc: In function 'int mpsort(int*, int)':
foo.cc:30:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^

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