运用赫夫曼编码的最优前缀码的贪心算法构造huffman树：

首先扫描输入文件，统计出现的字符以及每个字符出现的次数。每次取出现次数最小的那两个节点(node)合并成一个节点(node)，并且将累计数值相加作为新的接点的累计数值，最顶层的是根节点(root) -Huffman coding using optimal prefix code of the greedy algorithm constructs huffman tree: First, scan the input file, the characters appear as well as statistics the number of occurrences of each character. Take the minimum number of occurrences for each two nodes (node) into a single node (node), and the total value added as the cumulative number of new contacts, the top is the root node (root)