Compilare: user.cpp: In function ‘int main()’: user.cpp:93:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < v->size(); ++i) ^ user.cpp:96:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < v1->size(); ++i) ^ user.cpp:99:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < v2->size(); ++i) ^