Compilare: user.cpp: In function ‘void insert(trie*, char*)’: user.cpp:19:10: warning: NULL used in arithmetic [-Wpointer-arith] {if (*s==NULL) {t->nrapar++; return;} ^ user.cpp: In function ‘void remove(trie*, char*)’: user.cpp:28:10: warning: NULL used in arithmetic [-Wpointer-arith] {if (*s==NULL) {t->nrapar--; return;} ^ user.cpp: In function ‘int number(trie*, char*)’: user.cpp:38:13: warning: NULL used in arithmetic [-Wpointer-arith] if (*s==NULL) ^ user.cpp: In function ‘int prefix(trie*, char*, int)’: user.cpp:46:37: warning: NULL used in arithmetic [-Wpointer-arith] if (t->fii[s[0]-'a']==NULL||*s==NULL) ^ user.cpp: In function ‘int main()’: user.cpp:61:9: warning: NULL used in arithmetic [-Wpointer-arith] if (*s==NULL) continue; ^ user.cpp: In function ‘int number(trie*, char*)’: user.cpp:43:1: warning: control reaches end of non-void function [-Wreturn-type] } ^