问题描述：根据给定字符的使用频率，为其设计哈夫曼编码。

设计要求：

1．功能：求出n个字符的哈夫曼编码。

2．输入：输入n个字符和字符在电文中的使用频率。

3．输出：n个字符的哈夫曼编码。

-Problem Descr iption: According to the frequency of use given character, to design Huffman coding. Design requirements: 1. Function: Find the n characters Huffman coding. 2. Input: Enter the characters and character n in the frequency of use in the message. 3. Output: n characters Huffman coding.