霍夫曼编码的代码，代码读取一个名为1的txt文本并对其中的各个字母出现的次数进行统计，然后生成哈夫曼树并并返回哈夫曼编码-Huffman coding code, the code to read a txt text a number of times which is named and the letters appearing statistics, Huffman tree and then generates and returns Huffman coding