Compilare: user.cpp: In function ‘void Insert(TrieNode*, char*)’: user.cpp:27:15: warning: NULL used in arithmetic [-Wpointer-arith] if(*word == NULL) return; ^~~~ user.cpp: In function ‘void Erase(TrieNode*, char*)’: user.cpp:37:15: warning: NULL used in arithmetic [-Wpointer-arith] if(*word == NULL) return; ^~~~ user.cpp: In function ‘int CountApparitions(TrieNode*, char*)’: user.cpp:43:15: warning: NULL used in arithmetic [-Wpointer-arith] if(*word == NULL) { ^~~~ user.cpp: In function ‘int MaxCommonLength(TrieNode*, char*, int)’: user.cpp:62:15: warning: NULL used in arithmetic [-Wpointer-arith] if(*word == NULL || node->sons[*word - 'a'] == NULL || node->sons[*word - 'a']->wordCount == 0) { ^~~~