Compilare: user.cpp: In function ‘void solve(int, std::string)’: user.cpp:20:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < s.size (); ++ i) { ^ user.cpp:30:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (c < s.size () && s [c] == s [b]) { ^ user.cpp: In function ‘int main()’: user.cpp:71:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = B.size (); i < A.size () + B.size (); i ++) { ^