Compilare: user.cpp: In function ‘void DFS(int)’: user.cpp:141:13: warning: unused variable ‘cost’ [-Wunused-variable] int cost = my_heap.get_cost(); ^ user.cpp: In member function ‘void input_reader::advance()’: user.cpp:18:53: 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:30:49: 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 ); ^