Compilare: user.cpp: In function ‘int main()’: user.cpp:45:9: warning: array subscript has type ‘char’ [-Wchar-subscripts] f[s[i]]++; ^ user.cpp:49:14: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (ok[s[i]]) { ^ user.cpp:51:10: warning: array subscript has type ‘char’ [-Wchar-subscripts] f[s[i]]--; ^ user.cpp:57:35: warning: array subscript has type ‘char’ [-Wchar-subscripts] while (!st.empty() && f[st.top()] && st.top() > s[i]) { ^ user.cpp:59:15: warning: array subscript has type ‘char’ [-Wchar-subscripts] ok[st.top()] = false; ^ user.cpp:65:9: warning: array subscript has type ‘char’ [-Wchar-subscripts] f[s[i]]--; ^ user.cpp:67:15: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (!ok[s[i]]) { ^ user.cpp:71:11: warning: array subscript has type ‘char’ [-Wchar-subscripts] ok[s[i]] = true; ^