Compilare: user.cpp: In function ‘void Insert(Trie*, char*)’: user.cpp:21:13: warning: NULL used in arithmetic [-Wpointer-arith] if (*s==NULL) {T->Nr++; return;} ^ user.cpp: In function ‘void Remove(Trie*, char*)’: user.cpp:32:13: warning: NULL used in arithmetic [-Wpointer-arith] if (*s==NULL) {T->Nr--;return;} ^ user.cpp: In function ‘int Find(Trie*, char*)’: user.cpp:44:13: warning: NULL used in arithmetic [-Wpointer-arith] if (*s==NULL) return T->Nr; ^ user.cpp: In function ‘int Prefix(Trie*, char*, int)’: user.cpp:50:13: warning: NULL used in arithmetic [-Wpointer-arith] if (*s==NULL || T->fii[s[0]-'a']==NULL) return K; ^ user.cpp: In function ‘int main()’: user.cpp:65:17: warning: NULL used in arithmetic [-Wpointer-arith] if (*s==NULL) continue; ^ user.cpp: In function ‘int Find(Trie*, char*)’: user.cpp:46:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:55:35: 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:56:37: 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:63:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%c", &x, &c); ^ user.cpp:64:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/cc89j3TQ.o: In function `main': user.cpp:(.text.startup+0xce): warning: the `gets' function is dangerous and should not be used.