foo.cc: In function 'void dts::dfs(std::vector<double>)':
foo.cc:35:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (ll i=0;i<rec.size();i++)
                         ~^~~~~~~~~~~
foo.cc:36:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 for (ll j=i+1;j<rec.size();j++)
                               ~^~~~~~~~~~~
foo.cc:38:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     for (ll k=0,l=0;k<rec.size();k++)
                                     ~^~~~~~~~~~~
foo.cc: In function 'void dts::main()':
foo.cc:69:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%lf",&a[i]);
             ~~~~~^~~~~~~~~~~~~
foo.cc:73:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
                 scanf("%lf",&key);
                 ~~~~~^~~~~~~~~~~~

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