霍夫曼编解码，采用构造霍夫曼树进行编码；构造好霍夫曼树后解码的过程就比较简单了；只需通过霍夫曼树找到相应的叶子节点即可解码-Hoffman codec used to encode structural Huffman tree good Huffman tree structure after decoding process is relatively simple just find the leaf node can be decoded by the Huffman tree