Compilare: user.cpp: In constructor ‘trie_node::trie_node()’: user.cpp:15:22: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] cnt_children = NULL; cnt_words = NULL; ^ user.cpp:15:40: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] cnt_children = NULL; cnt_words = NULL; ^ user.cpp:16:43: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] back_node = NULL; cnt_occurrences = NULL; ^ user.cpp: In function ‘void insert_word(trie_node*, char*)’: user.cpp:26:18: warning: NULL used in arithmetic [-Wpointer-arith] if( *word == NULL ) { ^ user.cpp: In function ‘bool erase_word(trie_node*, char*)’: user.cpp:41:18: warning: NULL used in arithmetic [-Wpointer-arith] if( *word == NULL ) node -> cnt_words --; else ^ user.cpp:45:49: warning: NULL used in arithmetic [-Wpointer-arith] if( node != root && node -> cnt_children == NULL && node -> cnt_words == NULL ) { ^ user.cpp:45:78: warning: NULL used in arithmetic [-Wpointer-arith] if( node != root && node -> cnt_children == NULL && node -> cnt_words == NULL ) { ^ user.cpp: In function ‘bool find_word(trie_node*, char*)’: user.cpp:54:18: warning: NULL used in arithmetic [-Wpointer-arith] if( *word == NULL ) ^ user.cpp: In function ‘int count_word(trie_node*, char*)’: user.cpp:64:18: warning: NULL used in arithmetic [-Wpointer-arith] if( *word == NULL ) ^ user.cpp: In function ‘int count_occurrences(trie_node*, char*)’: user.cpp:74:18: warning: NULL used in arithmetic [-Wpointer-arith] if( *word == NULL ) ^ user.cpp: In function ‘int longest_prefix(trie_node*, char*, int)’: user.cpp:84:18: warning: NULL used in arithmetic [-Wpointer-arith] if( *word == NULL ) ^ user.cpp: In function ‘void reset_machine(trie_node*)’: user.cpp:94:29: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] node -> cnt_occurrences = NULL; ^ user.cpp: In function ‘void build_occurrences(trie_node*, char*)’: user.cpp:138:34: warning: NULL used in arithmetic [-Wpointer-arith] for( *word = *word; *word != NULL; word ++ ) { ^ user.cpp: In function ‘void build_partial_sum(trie_node*)’: user.cpp:153:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]