Compilare: user.cpp: In function ‘void add_trie(trie*, char*)’: user.cpp:22:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) ^ user.cpp: In function ‘bool delete_trie(trie*, char*)’: user.cpp:39:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) ^ user.cpp: In function ‘int find_trie(trie*, char*)’: user.cpp:61:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) ^ user.cpp: In function ‘int longest_prefix(trie*, char*)’: user.cpp:72:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL || aux->son[code(*s)] == NULL) ^ user.cpp: In function ‘int main()’: user.cpp:83:12: warning: variable ‘f’ set but not used [-Wunused-but-set-variable] int q, f; ^ user.cpp:80:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trie.in", "r", stdin); ^ user.cpp:81:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trie.out", "w", stdout); ^ user.cpp:87:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ user.cpp:100:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/cc3HSb36.o: In function `main': user.cpp:(.text.startup+0xb5): warning: the `gets' function is dangerous and should not be used.