Compilare: user.cpp: In function ‘void ins(nod*, std::string)’: user.cpp:17:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); ++i) ^ user.cpp: In function ‘void del(nod*, std::string)’: user.cpp:30:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); ++i) ^ user.cpp: In function ‘int out(nod*, std::string)’: user.cpp:40:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); ++i) ^ user.cpp: In function ‘int pre(nod*, std::string)’: user.cpp:50:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( ;lung_pref < s.size() && n->fii[s[lung_pref]-'a'] && n->fii[s[lung_pref]-'a']->aparitii ; ) ^