Compilare: user.cpp: In function ‘void pre_line(int)’: user.cpp:70:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < aux.size(); i++) ^ user.cpp: In function ‘void pre_column(int)’: user.cpp:81:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < aux.size(); i++) ^ user.cpp: In function ‘void solve(int, int)’: user.cpp:86:9: warning: unused variable ‘i’ [-Wunused-variable] int i, xx, yy; ^ user.cpp:86:12: warning: unused variable ‘xx’ [-Wunused-variable] int i, xx, yy; ^ user.cpp:86:16: warning: unused variable ‘yy’ [-Wunused-variable] int i, xx, yy; ^ user.cpp: In function ‘int main()’: user.cpp:100:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("zoro.out","w",stdout); ^ user.cpp: In constructor ‘Buffer::Buffer(std::__cxx11::string, int)’: user.cpp:20:46: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(name.c_str(), "r", stdin); ^ user.cpp: In member function ‘void Buffer::refill()’: user.cpp:52:43: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(&data[0], 1, dim, stdin); ^