Compilare: user.cpp: In function ‘int main()’: user.cpp:14:11: warning: array subscript has type ‘char’ [-Wchar-subscripts] f[s[i]]++; ^ user.cpp:19:29: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (ch != last && f[ch] > 0) { ^ user.cpp:22:13: warning: array subscript has type ‘char’ [-Wchar-subscripts] f[ch]--; ^ user.cpp:7:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("ordine.in", "r", stdin); ^ user.cpp:8:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("ordine.out", "w", stdout); ^ user.cpp:11:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s", s); ^