Compilare: user.cpp: In function ‘void add(Trie*&, const string&, int)’: user.cpp:17:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (word_index == word.size()) { ^ user.cpp: In function ‘bool remove(Trie*&, const string&, int)’: user.cpp:29:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (word_index == word.size()) { ^ user.cpp: In function ‘int search(Trie*&, const string&, int)’: user.cpp:43:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (word_index == word.size()) { ^ user.cpp: In function ‘int query(Trie*&, const string&, int, int)’: user.cpp:54:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (word_index == word.size()) { ^ user.cpp: In function ‘int main()’: user.cpp:69:13: warning: unused variable ‘ret’ [-Wunused-variable] int op, ret; ^ user.cpp:65:35: 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:66:37: 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); ^