Compilare: user.cpp: In function ‘int main()’: user.cpp:39:28: warning: NULL used in arithmetic [-Wpointer-arith] while(v[i].s[j] != NULL && v[i-1].s[j] != NULL && v[i].s[j] == v[i-1].s[j]) ^ user.cpp:39:51: warning: NULL used in arithmetic [-Wpointer-arith] while(v[i].s[j] != NULL && v[i-1].s[j] != NULL && v[i].s[j] == v[i-1].s[j]) ^ user.cpp:22:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dictree.in", "r", stdin); ^ user.cpp:23:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dictree.out", "w", stdout); ^ user.cpp:27:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &n); ^ user.cpp:30:21: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(v[i].s); ^ /tmp/ccJwU4h5.o: In function `main': user.cpp:(.text.startup+0x80): warning: the `gets' function is dangerous and should not be used.