Compilare: user.cpp: In function ‘int main()’: user.cpp:89:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int j = 0; j < L2[i].size(); j ++ ) { ^ user.cpp: In member function ‘void input_reader::advance()’: user.cpp:24:53: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread( buffer, SIZE, 1, input_file ); ^ user.cpp: In constructor ‘input_reader::input_reader(const char*, const char*)’: user.cpp:36:49: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread( buffer, SIZE, 1, input_file ); ^