霍夫曼编码与解码，功能：输入任意符号和权值，构建霍夫曼树，输出霍夫曼编码，计算平均码长，输入任意编码进行解码，错误提示。-Huffman encoding and decoding functions: Enter any symbols and weights to build Huffman tree, the output Huffman code to calculate the average code length, input Into any codec decoding e