Compilare: user.cpp: In function ‘void mul(std::vector<int>&, int)’: user.cpp:19:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int i = 0; i < h.size(); i ++ ) { ^ user.cpp: In function ‘void add(std::vector<int>&, std::vector<int>)’: user.cpp:31:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( i = 0; i < b.size(); i ++ ) { ^ user.cpp:32:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if ( a.size() <= i ) ^ user.cpp:42:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if ( a.size() <= i ) ^