foo.cc: In function 'void dfs(int, int)':
foo.cc:16:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int j=0;j<dislike[i].size();j++){
              ~^~~~~~~~~~~~~~~~~~

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