foo.cc: In function 'void SPFA1()':
foo.cc:22:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0; i<E1[x].size(); i++) {
                      ~^~~~~~~~~~~~~
foo.cc: In function 'void SPFA2()':
foo.cc:47:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0; i<E2[x].size(); i++) {
                      ~^~~~~~~~~~~~~

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