Compilare: user.cpp: In function ‘int frecv(Trie*, char*)’: user.cpp:41:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(s);root = root->fii[gn(s[i++])]) ^ user.cpp:40:9: warning: unused variable ‘n’ [-Wunused-variable] int n=strlen(s),i; ^ user.cpp: In function ‘int main()’: user.cpp:82:33: 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:83:35: 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:88:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/cclQ4kTG.o: In function `main': user.cpp:(.text.startup+0x75): warning: the `gets' function is dangerous and should not be used.