foo.cc: In function 'void dfs1(int, int)':
foo.cc:12:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for( int i = 0; i < g[ x ].size(); i++ )
                  ~~^~~~~~~~~~~~~~~
foo.cc: In function 'void dfs2(int, int)':
foo.cc:46:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for( int i = 0; i < g[ x ].size(); i++ )
                  ~~^~~~~~~~~~~~~~~

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

{"receive":"2020-07-30T13:43:09.385Z","handle":"2020-07-30T13:43:09.385Z","cache_start":"2020-07-30T13:43:09.413Z","read_cases":"2020-07-30T13:43:09.546Z","judge":"2020-07-30T13:43:09.550Z","done":"2020-07-30T13:43:11.543Z"}