foo.cc: In function 'long long int dfs(long long int)':
foo.cc:18:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
foo.cc: In function 'int main()':
foo.cc:21:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&t);
  ~~~~~^~~~~~~~~
foo.cc:24:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld",&n);
   ~~~~~^~~~~~~~~~~

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

{"receive":"2020-08-10T11:53:46.395Z","handle":"2020-08-10T11:53:46.395Z","cache_start":"2020-08-10T11:53:46.403Z","read_cases":"2020-08-10T11:53:46.534Z","judge":"2020-08-10T11:53:46.535Z","done":"2020-08-10T11:53:46.777Z"}