Compilare: user.cpp: In function ‘void insertTrie(Trie*, char*)’: user.cpp:21:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL) { ^ user.cpp: In function ‘int removeTrie(Trie*, char*)’: user.cpp:35:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL) { ^ user.cpp: In function ‘int countTrie(Trie*, char*)’: user.cpp:58:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL) { ^ user.cpp: In function ‘int maxPrefixTrie(Trie*, char*, int)’: user.cpp:69:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL || !node-> child[*s - 'a']) { ^ user.cpp: In function ‘int main()’: user.cpp:77:36: 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:78:38: 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:80:13: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (s); ^ user.cpp:89:17: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (s); ^ /tmp/ccD2auUy.o: In function `main': user.cpp:(.text.startup+0x54): warning: the `gets' function is dangerous and should not be used.