利用二叉树结构实现赫夫曼编/解码器。

基本要求：

1、初始化：能够对输入的任意长度的字符串s进行统计，统计每个字符的频度，并建立赫夫曼树

2、建立编码表：利用已经建好的赫夫曼树进行编码，并将每个字符的编码输出。

3、编码：根据编码表对输入的字符串进行编码，并将编码后的字符串输出。

4、译码:利用已经建好的赫夫曼树对编码后的字符串进行译码，并输出译码结果。

5、打印：以直观的方式打印赫夫曼树（选作）

6、计算输入的字符串编码前和编码后的长度，并进行分析，讨论赫夫曼编码的压缩效果。

-Using binary tree structure to achieve Huffman encoder/decoder.

Basic requirements:

1 Initialization: the ability to input a string of arbitrary length s statistical, statistical frequency of each character, and the establishment of Huffman tree

2, the coding table: the use of the Huffman tree has been built to encode, and encoding each character output.

3, code: According to the code table to encode the input string and output the encoded string.

4, decoding: use of the Huffman tree has been built on the encoded string decoding, and outputs decoding result.

5, print: the intuitive way to print Huffman tree (chosen as)

6 to calculate the input code string length before and after coding, and analysis, discussion of Huffman coding compression.