First of all, to establish huffman tree, its main idea is right outside the large node near the root, the right to stay away from small root.

• 详细说明： 本算法的作用是利用建立的huffman编码进行编码和译码。首先要建立huffman树，其主要的思想是权大的外结点靠近根，权小的远离根。