设计一个哈夫曼编码、译码系统。对一个ASCII编码的文本文件中的字符进行哈夫曼编码，生成编码文件；反过来，可将编码文件译码还原为一个文本文件。
（1）从文件中读入任意一篇英文短文（文件为ASCII编码，扩展名为txt）；
（2）统计并输出不同字符在文章中出现的频率（空格、换行、标点等也按字符处理）；
（3）根据字符频率构造哈夫曼树，并给出每个字符的哈夫曼编码；
（4）图形化输出哈夫曼树、哈夫曼编码；
（5）将文本文件利用哈夫曼树进行编码，存储成压缩文件（编码文件后缀名.huf）
（6）用哈夫曼编码来存储文件，并和输入文本文件大小进行比较，计算文件压缩率；
（7）进行译码，将huf文件译码为ASCII编码的txt文件，与原txt文件进行比较。(Design a Huffman coding and decoding system. Encoding the characters in an ascii - encoded text file, generating the encoding file; In turn, the encoded file decoding can be restored to a text file.
( 1 ) read any English short passage from the file ( the file is ascii and the extension is txt );
( 2 ) statistics and output the frequency of different characters in the article ( space, line breaks, punctuation, etc. also by character );
( 3 ) Huffman tree is constructed according to the character frequency, and Huffman coding of each character is given.
( 4 ) graphic output Huffman tree, Huffman coding;
( 5 ) the text file is encoded using Huffman tree and stored as compressed file ( encoded file suffix. huf )
( 6 ) the Huffman coding is used to store the file, and compared with the input text file size, the compression ratio of the file is calculated.
( 7 ) decode, decode the huf file into ascii - encoded txt file, and compare it with the original txt file.)