Compilare: user.cpp: In function ‘int main()’: user.cpp:42:17: warning: array subscript has type ‘char’ [-Wchar-subscripts] f[ s[i] ] ++; ^ user.cpp:37:37: 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:38:39: 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:39:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s + 1); ^ /tmp/ccRQdTd7.o: In function `main': user.cpp:(.text.startup+0x54): warning: the `gets' function is dangerous and should not be used.