foo.cc: In function 'bool bfs(int, int)':
foo.cc:72:21: 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:173:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < v_flows[cur].size(); i++)
                   ~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:205:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i = 0; i < v_flows[cur].size(); i++)
                    ~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:101:6: warning: unused variable 'value' [-Wunused-variable]
  int value = 0;
      ^~~~~

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

{"receive":"2020-08-12T11:56:56.248Z","handle":"2020-08-12T11:56:56.248Z","cache_start":"2020-08-12T11:56:56.256Z","read_cases":"2020-08-12T11:56:56.387Z","judge":"2020-08-12T11:56:56.395Z","done":"2020-08-12T11:56:57.570Z"}