霍夫曼编码:最优子结构性质的证明方法,贪心法的设计思想并能熟练运用,前缀编码的概念，理解数据压缩的基本方法. -Huffman coding: the best evidence of the nature of sub-structure method, the greedy method of design and can skillfully use the concept of prefix code, understand the basic method of data comp