Compilare: user.cpp: In function ‘int main()’: user.cpp:32:31: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (!ap[str[j]]) ++app[str[j]]; ^ user.cpp:32:46: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (!ap[str[j]]) ++app[str[j]]; ^ user.cpp:33:26: warning: array subscript has type ‘char’ [-Wchar-subscripts] ap[str[j]] = true; ^ user.cpp:13:39: 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:14:41: 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); ^ user.cpp:16:35: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets (str + 1, 100010, stdin); ^ In file included from /usr/include/stdio.h:936:0, from /usr/include/c++/5/cstdio:42, from user.cpp:1: In function ‘char* fgets(char*, int, FILE*)’, inlined from ‘int main()’ at user.cpp:16:35: /usr/include/bits/stdio2.h:261:58: warning: call to ‘__fgets_chk_warn’ declared with attribute warning: fgets called with bigger size than length of destination buffer return __fgets_chk_warn (__s, __bos (__s), __n, __stream); ^