Compilare: user.cpp: In function ‘int main()’: user.cpp:17:17: warning: array subscript has type ‘char’ [-Wchar-subscripts] fr[s[dr]]++; ^ user.cpp:18:21: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (fr[s[dr]]==1) ^ user.cpp:27:28: warning: array subscript has type ‘char’ [-Wchar-subscripts] while (fr[s[dr]]>=1) ^ user.cpp:29:25: warning: array subscript has type ‘char’ [-Wchar-subscripts] fr[s[dr]]--; ^