Compilare: user.cpp: In function ‘void insert(trie*, char*)’: user.cpp:14:13: warning: NULL used in arithmetic [-Wpointer-arith] {if(*s==NULL) ^ user.cpp: In function ‘bool remove(trie*, char*)’: user.cpp:25:13: warning: NULL used in arithmetic [-Wpointer-arith] {if(*s==NULL) ^ user.cpp: In function ‘int count(trie*, char*)’: user.cpp:39:13: warning: NULL used in arithmetic [-Wpointer-arith] {if(*s==NULL) ^ user.cpp: In function ‘int prefix(trie*, char*)’: user.cpp:47:13: warning: NULL used in arithmetic [-Wpointer-arith] {if(*s==NULL) ^ user.cpp: In function ‘int main()’: user.cpp:59:20: warning: format ‘%s’ expects argument of type ‘char*’, but argument 2 has type ‘char (*)[21]’ [-Wformat=] while(scanf("%s",&s)!=EOF) ^ user.cpp:54:31: 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:55:32: 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:57:15: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x); ^ user.cpp:74:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x); ^