foo.cc: In function 'void s(int)':
foo.cc:8:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[x].size();i++){
               ^

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

{"receive":"2020-04-03T01:10:45.405Z","handle":"2020-04-03T01:10:45.405Z","cache_start":"2020-04-03T01:10:45.412Z","read_cases":"2020-04-03T01:10:46.246Z","judge":"2020-04-03T01:10:46.247Z","done":"2020-04-03T01:10:48.069Z"}