Compilare: user.cpp: In constructor ‘Trie::Trie()’: user.cpp:18:42: warning: passing NULL to non-pointer argument 2 of ‘void* memset(void*, int, size_t)’ [-Wconversion-null] memset(son, NULL, sizeof(son)); ^ user.cpp: In function ‘void Ins_A(Trie*, char*, int&)’: user.cpp:34:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL) ^ user.cpp: In function ‘void Ins_B(Trie*, char*, int&)’: user.cpp:55:15: warning: NULL used in arithmetic [-Wpointer-arith] if (*s == NULL || nod->son[*s - 'a'] == NULL) ^ user.cpp: In function ‘int main()’: user.cpp:84:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < strlen(S) - 1; j ++) ^ user.cpp:94:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < strlen(S) - 1; j ++) ^