Compilare: main.cpp: In function 'void op1(trie*, char*)': main.cpp:27:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL) ^~~~ main.cpp: In function 'int op2(trie*, char*)': main.cpp:42:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL) ^~~~ main.cpp: In function 'int nrap(trie*, char*)': main.cpp:59:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL) ^~~~ main.cpp: In function 'int lung(trie*, char*)': main.cpp:68:42: warning: NULL used in arithmetic [-Wpointer-arith] if (nod->fii[*s - 'a'] == 0 || *s == NULL) ^~~~