Compilare: user.cpp: In constructor ‘trie::trie()’: user.cpp:15:19: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] cnt_words = NULL; ^ user.cpp:16:22: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] cnt_children = NULL; ^ user.cpp: In function ‘int delete_word(trie*, char*)’: user.cpp:48:30: warning: NULL used in arithmetic [-Wpointer-arith] if( Node -> cnt_words == NULL && Node -> cnt_children == NULL && Node != Root ) { ^ user.cpp:48:62: warning: NULL used in arithmetic [-Wpointer-arith] if( Node -> cnt_words == NULL && Node -> cnt_children == NULL && Node != Root ) { ^ user.cpp: In function ‘int main()’: user.cpp:80:37: 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:81:37: 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:84:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf( "%s", String ); ^