Compilare: user.cpp: In function ‘int main()’: user.cpp:15:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=1;i<a.size();i++) ^ user.cpp:26:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<b.size();i++) ^ user.cpp:32:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (pos+1==a.size()) ^ user.cpp:39:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<r.size();i++) ^