Compilare: user.cpp: In function ‘int main()’: user.cpp:78:41: warning: unused variable ‘ck’ [-Wunused-variable] int k = 0, n = strlen (ss), ck = -1; ^ user.cpp:26:36: 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:27:38: 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:30:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d ", &op); ^ user.cpp:31:14: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (ss); ^ user.cpp:125:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d ", &op); ^ user.cpp:126:18: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (ss); ^ /tmp/cc8Sy2lf.o: In function `main': user.cpp:(.text.startup+0x6a): warning: the `gets' function is dangerous and should not be used.