Compilare: user.cpp: In function ‘int main()’: user.cpp:34:31: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (!used[s[j]] && s[j] < 'a' + fixed) ^ user.cpp:36:26: warning: array subscript has type ‘char’ [-Wchar-subscripts] used[s[j]] = 1; ^ user.cpp:40:26: warning: array subscript has type ‘char’ [-Wchar-subscripts] used[s[j]] = 0; ^ user.cpp:19:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("smooth2.in","r",stdin); ^ user.cpp:20:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("smooth2.out","w",stdout); ^