Compilare: user.cpp: In function ‘void insert(trie*, int)’: user.cpp:24: warning: NULL used in arithmetic user.cpp: In function ‘int del(trie*, int)’: user.cpp:39: warning: NULL used in arithmetic user.cpp: In function ‘int nr_ap(trie*, int)’: user.cpp:58: warning: NULL used in arithmetic user.cpp: In function ‘int prefix(trie*, int, int)’: user.cpp:69: warning: NULL used in arithmetic user.cpp: In function ‘int main()’: user.cpp:75: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:76: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:82: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result