Compilare: main.cpp: In function 'void add(node*, char*)': main.cpp:22:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*word == NULL) { ^~~~ main.cpp: In function 'int count_app(node*, char*)': main.cpp:35:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*word == NULL) ^~~~ main.cpp: In function 'int delete_app(node*, char*)': main.cpp:44:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*word == NULL) { ^~~~ main.cpp: In function 'int count_cp(node*, char*)': main.cpp:66:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*word == NULL || curr_node -> son[idx] == NULL) ^~~~ main.cpp: In function 'int count_app(node*, char*)': main.cpp:41:1: warning: control reaches end of non-void function [-Wreturn-type] } ^