Compilare: user.cpp: In member function ‘void MaximumMatching::make_matching()’: user.cpp:139:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < used -> size(); ++i) ^ user.cpp: In member function ‘void MaximumMatching::make_size()’: user.cpp:157:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < left_to_right -> size(); ++i) ^ user.cpp: In function ‘int main(int, const char**)’: user.cpp:214:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < left -> size(); ++i) ^