Compilare: user.cpp: In function ‘int main()’: user.cpp:18:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s.size(); ++i) ^ user.cpp:23:9: warning: array subscript has type ‘char’ [-Wchar-subscripts] F[s[i]]=mx+1; ^ user.cpp:27:9: warning: array subscript has type ‘char’ [-Wchar-subscripts] u[s[i]]=mn+1; ^