foo.cc: In function 'bool bfs(int, int)':
foo.cc:71:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < v_flows[front].size(); j++)
                   ~~^~~~~~~~~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:194:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < v_flows[cur].size(); i++)
                   ~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:228:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i = 0; i < v_flows[cur].size(); i++)
                    ~~^~~~~~~~~~~~~~~~~~~~~

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

{"receive":"2020-08-12T09:12:42.912Z","handle":"2020-08-12T09:12:42.912Z","cache_start":"2020-08-12T09:12:42.919Z","read_cases":"2020-08-12T09:12:43.049Z","judge":"2020-08-12T09:12:43.051Z","done":"2020-08-12T09:12:43.682Z"}