Compilare: user.cpp: In function ‘int add(int, int)’: user.cpp:41:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘void df(int)’: user.cpp:45:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k=0;k<v[x].size();k++) ^ user.cpp: In function ‘int main()’: user.cpp:73:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k=0;k<v[i].size();k++) ^ user.cpp:79:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k=0;k<v[i].size();k++) ^