Compilare: user.cpp: In function ‘int main()’: user.cpp:33:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1; i<a.size(); ++i) ^ user.cpp:45:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0; i < b.size(); ++i) ^ user.cpp:54:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k==a.size()) ^ user.cpp:65:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < positions.size(); ++i) ^