Compilare: user.cpp: In function ‘int main()’: user.cpp:62:29: 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:63:31: 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:66:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d ",&tip); gets(s+1); n=strlen(s+1); ^ user.cpp:66:33: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d ",&tip); gets(s+1); n=strlen(s+1); ^ /tmp/ccmUl31Y.o: In function `main': user.cpp:(.text.startup+0xbb): warning: the `gets' function is dangerous and should not be used.