foo.cc: In function 'int main()':
foo.cc:15:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&n,&m);
                        ^
foo.cc:17:47: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int opt,u,v;scanf("%d%d%d",&opt,&u,&v);
                                               ^

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

{"receive":"2020-03-31T09:54:55.042Z","handle":"2020-03-31T09:54:55.042Z","cache_start":"2020-03-31T09:54:55.052Z","read_cases":"2020-03-31T09:54:55.179Z","judge":"2020-03-31T09:54:55.180Z","done":"2020-03-31T09:54:57.043Z"}