Compilare: user.cpp: In function ‘void add(Trie*, char*)’: user.cpp:18:12: warning: NULL used in arithmetic [-Wpointer-arith] if(*s==NULL){ ^ user.cpp: In function ‘int count(Trie*, char*)’: user.cpp:30:12: warning: NULL used in arithmetic [-Wpointer-arith] if(*s==NULL){ ^ user.cpp: In function ‘bool remove(Trie*, char*)’: user.cpp:39:12: warning: NULL used in arithmetic [-Wpointer-arith] if(*s==NULL){ ^ user.cpp: In function ‘int pref(Trie*, char*)’: user.cpp:59:12: warning: NULL used in arithmetic [-Wpointer-arith] if(*s==NULL||node->son[s[0]-'a']==NULL){ ^ user.cpp: In function ‘int main()’: user.cpp:69:32: warning: format ‘%s’ expects argument of type ‘char*’, but argument 3 has type ‘char (*)[21]’ [-Wformat=] while(scanf("%d %s",&tip,&s)!=EOF){ ^ user.cpp:80:13: warning: variable ‘x’ set but not used [-Wunused-but-set-variable] int x; ^ user.cpp:66:33: 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:67:35: 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); ^