foo.cc: In function 'int main()':
foo.cc:31:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&m);
  ~~~~~^~~~~~~~~~~~~~
foo.cc:32:61: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1; i<=m; i++) scanf("%d%d",&x,&y),cd[x]++,rd[y]++,add(x,y);
                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~

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

{"receive":"2020-05-27T06:25:05.120Z","handle":"2020-05-27T06:25:05.120Z","cache_start":"2020-05-27T06:25:05.127Z","read_cases":"2020-05-27T06:25:08.056Z","judge":"2020-05-27T06:25:08.057Z","done":"2020-05-27T06:25:09.077Z"}