Compilare: main.cpp: In function 'void addWord(trie*, char*)': main.cpp:17:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) ^~~~ main.cpp: In function 'int deleteWord(trie*, char*)': main.cpp:31:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) ^~~~ main.cpp: In function 'int nrAp(trie*, char*)': main.cpp:47:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) ^~~~ main.cpp: In function 'int prefix(trie*, char*, int)': main.cpp:55:14: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL || nod->fiu[*s - 'a'] == 0) ^~~~ main.cpp: In function 'int main()': main.cpp:61:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("trie.in", "r", stdin); ^ main.cpp:62:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("trie.out", "w", stdout); ^ main.cpp:67:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%s\n" , s); ^