Compilare: user.cpp: In function ‘void back(int)’: user.cpp:17:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v[k].size(); i++) ^ user.cpp:24:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v[k].size(); i++) ^ user.cpp: In function ‘int getnr(int&)’: user.cpp:54:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^