Compilare: user.cpp: In function ‘void trend(int, int)’: user.cpp:22:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0 ; i < l.size(); ++i) ^ user.cpp:54:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0 ; i < l.size() ; ++i) ^ user.cpp:71:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0 ; i < aux.size() ; ++i) ^ user.cpp:72:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0 ; j < aux.size() ; ++j) ^