Compilare: user.cpp: In function ‘int main()’: user.cpp:45:15: warning: array subscript has type ‘char’ [-Wchar-subscripts] f[s[i]]++; ^ user.cpp:49:19: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(ok[s[i]]) ^ user.cpp:52:40: warning: array subscript has type ‘char’ [-Wchar-subscripts] while(!st.empty() && f[st.top()] && st.top() > s[i]) { ^ user.cpp:54:24: warning: array subscript has type ‘char’ [-Wchar-subscripts] ok[st.top()] = false; ^ user.cpp:60:15: warning: array subscript has type ‘char’ [-Wchar-subscripts] f[s[i]]--; ^ user.cpp:62:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(!ok[s[i]]) { ^ user.cpp:66:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] ok[s[i]] = true; ^