说明：  采用哈夫曼编码思想实现某个文件的压缩和解压缩功能,并提供压缩前后的文件占用空间之比．要求：(1)压缩前文件的规模应不小于５Ｋ．(2)提供原文件与压缩后文件的相同性比较功能．
(achieving a file compression function, Compression and provide documents before and after the occupation of space ratio. : (1) compressed documents before the scale should be no less than 5 K. (2) the original of the document after document compression and the same comparison function.)