/in/foo.cc: In function 'void SPFA()':
/in/foo.cc:61:27: 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 BFS()':
/in/foo.cc:84:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < E[u].size(); i++) {
                         ~~^~~~~~~~~~~~~