Compilare: user.cpp: In member function ‘void Trie::Change(char*, long int)’: user.cpp:20:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(long i=0;i<strlen(s);i++){ ^ user.cpp: In member function ‘long int Trie::Count(char*)’: user.cpp:30:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(long i=0;i<strlen(s);i++){ ^ user.cpp: In member function ‘long int Trie::Check(char*)’: user.cpp:39:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(long i=0;i<strlen(s);i++){ ^ user.cpp: In function ‘int main()’: user.cpp:56:33: 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:57:35: 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:62:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld %s\n",&op,s); ^