Compilare: user.cpp: In function ‘int main()’: user.cpp:184:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < roots.size(); i++) ^ user.cpp: In function ‘char gchar()’: user.cpp:20:47: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] cnt = 0, fread(buff, buffer, 1, stdin); ^ user.cpp: In function ‘int main()’: user.cpp:146:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sortop.in", "r", stdin); ^ user.cpp:147:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sortop.out", "w", stdout); ^