/in/foo.cc: In function 'void spfa1()':
/in/foo.cc:20:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i=0; i<e[u].size(); ++i) {
                 ~^~~~~~~~~~~~
/in/foo.cc: In function 'void spfa2()':
/in/foo.cc:45:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i=0; i<re[u].size(); ++i) {
                 ~^~~~~~~~~~~~~