Compilare: user.cpp: In function ‘int main()’: user.cpp:24:30: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (used[s[j]] == 0) ^ user.cpp:25:47: warning: array subscript has type ‘char’ [-Wchar-subscripts] cnt[s[j]-'a']++, used[s[j]] = 1; ^ user.cpp:29:26: warning: array subscript has type ‘char’ [-Wchar-subscripts] used[s[j]] = 0; ^ user.cpp:11:36: 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:12:38: 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); ^