Compilare: user.cpp: In function ‘int main()’: user.cpp:54:61: warning: array subscript has type ‘char’ [-Wchar-subscripts] while(top > 0 && ch < str[top - 1] && fr1[str[top - 1]] > fr2[str[top - 1]]) { ^ user.cpp:54:81: warning: array subscript has type ‘char’ [-Wchar-subscripts] while(top > 0 && ch < str[top - 1] && fr1[str[top - 1]] > fr2[str[top - 1]]) { ^ user.cpp:55:27: warning: array subscript has type ‘char’ [-Wchar-subscripts] --fr1[str[top - 1]]; ^ user.cpp:67:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(fr3[str[i]] < fr2[str[i]]) { ^ user.cpp:67:34: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(fr3[str[i]] < fr2[str[i]]) { ^ user.cpp:69:19: warning: array subscript has type ‘char’ [-Wchar-subscripts] fr3[str[i]]++; ^