Compilare: user.cpp: In function ‘int main()’: user.cpp:45:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) ^ user.cpp:52:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) ^ user.cpp:55:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = i+1; j < s.size(); j++) ^