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++) {
                      ~^~~~~~~~~~~~~

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