Compilare: user.cpp: In constructor ‘trie::trie()’: user.cpp:20:36: warning: passing NULL to non-pointer argument 2 of ‘void* memset(void*, int, size_t)’ [-Wconversion-null] memset(fiu,NULL,sizeof(fiu)); ^ user.cpp: In member function ‘void trie::ins(char*)’: user.cpp:27:16: warning: NULL used in arithmetic [-Wpointer-arith] if(*s==NULL) ^ user.cpp: In member function ‘bool trie::del(char*)’: user.cpp:50:16: warning: NULL used in arithmetic [-Wpointer-arith] if(*s==NULL) ^ user.cpp: In member function ‘int trie::que(char*)’: user.cpp:74:18: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL) ^ user.cpp: In member function ‘int trie::pre(char*, int)’: user.cpp:91:18: warning: NULL used in arithmetic [-Wpointer-arith] if(*s == NULL || this->fiu[CH]==0) ^ user.cpp: In function ‘int main()’: user.cpp:119:11: warning: unused variable ‘fin’ [-Wunused-variable] FILE *fin,*fout; ^ user.cpp:119:16: warning: unused variable ‘fout’ [-Wunused-variable] FILE *fin,*fout; ^ user.cpp:121:35: 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); ^ user.cpp:122:35: 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); ^ user.cpp:130:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s",s); ^