说明：  哈夫曼树的存储和哈夫曼编码的存储 在哈夫曼树HT[1..n] 搜索最大权值和最小权值并用s1,s2 返回它们的下标
(Huffman tree storage and Huffman coding is stored in the Huffman tree HT [1 .. n] the right to search the maximum and minimum weights and use s1, s2 return their subscript)