哈弗曼树的算法编码，理解这个以后可以看看突变压缩之类的书籍，会很有帮助的-Ha Fuman tree algorithm code, understand the future can look like mutant compressed books will be helpful

输入一段数据，实现哈弗曼树的生成，并输出哈弗曼编码。-Enter a data to achieve Huffman tree generation, and outputs the Huffman coded.