Compilare: main.cpp: In function 'void insert(node*, char*)': main.cpp:27:14: warning: NULL used in arithmetic [-Wpointer-arith] 27 | if(*p == NULL) | ^~~~ main.cpp: In function 'void del(node*, char*)': main.cpp:43:14: warning: NULL used in arithmetic [-Wpointer-arith] 43 | if(*p == NULL) | ^~~~ main.cpp: In function 'long long int find(node*, char*)': main.cpp:51:14: warning: NULL used in arithmetic [-Wpointer-arith] 51 | if(*p == NULL) | ^~~~ main.cpp: In function 'long long int lpref(node*, char*)': main.cpp:63:14: warning: NULL used in arithmetic [-Wpointer-arith] 63 | if(*p == NULL || n->children[p[0]-'a'] == NULL) | ^~~~