foo.cc: In function 'int main()':
foo.cc:19:50: warning: format '%lld' expects argument of type 'long long int', but argument 2 has type 'int' [-Wformat=]
                 if(num[i]==1) printf("+x^%lld", j);
                                                  ^
foo.cc:20:51: warning: format '%lld' expects argument of type 'long long int', but argument 2 has type 'int' [-Wformat=]
                 if(num[i]==-1) printf("-x^%lld", j);
                                                   ^
foo.cc:22:61: warning: format '%lld' expects argument of type 'long long int', but argument 3 has type 'int' [-Wformat=]
                 if(num[i]>0) printf("+%lldx^%lld", num[i], j);
                                                             ^
foo.cc:23:60: warning: format '%lld' expects argument of type 'long long int', but argument 3 has type 'int' [-Wformat=]
                 if(num[i]<0) printf("%lldx^%lld", num[i], j);
                                                            ^
foo.cc:5:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld", &n);
     ~~~~~^~~~~~~~~~~~
foo.cc:7:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%lld", &num[i]);
         ~~~~~^~~~~~~~~~~~~~~~~

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