Compilare: user.cpp: In function ‘void add(Trie*, char*)’: user.cpp:14:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) { ^ user.cpp: In function ‘bool del(Trie*, char*)’: user.cpp:25:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) nod->cnt--; ^ user.cpp: In function ‘int ap(Trie*, char*)’: user.cpp:37:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) return nod->cnt; ^ user.cpp: In function ‘int pref(Trie*, char*, int)’: user.cpp:42:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) return k; ^ user.cpp: In function ‘int main()’: user.cpp:48:35: 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:49:37: 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:52:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &k); scanf("%s\n", s); ^ user.cpp:52:42: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &k); scanf("%s\n", s); ^