Compilare: user.cpp: In function ‘void add(trie*, int)’: user.cpp:31:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p == t.size()) ^ user.cpp: In function ‘void mark(trie*, int)’: user.cpp:45:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p == s.size()) return; ^ user.cpp: In function ‘int main()’: user.cpp:68:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ahocorasick.in" , "r" , stdin); ^ user.cpp:69:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ahocorasick.out" , "w" , stdout); ^