Compilare: user.cpp: In function ‘int main()’: user.cpp:54:16: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(fr3[ch] < fr2[ch]) { ^ user.cpp:54:26: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(fr3[ch] < fr2[ch]) { ^ user.cpp:55:63: 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:55:83: 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:56:29: warning: array subscript has type ‘char’ [-Wchar-subscripts] --fr1[str[top - 1]]; ^ user.cpp:57:29: warning: array subscript has type ‘char’ [-Wchar-subscripts] --fr3[str[top - 1]]; ^ user.cpp:61:17: warning: array subscript has type ‘char’ [-Wchar-subscripts] ++fr3[ch]; ^