求Huffman编码输入字符串，求出编码输入一段编码，实现译码，并设计主函数测试该类

以下是一个Huffman编码的示例代码，包括编码和译码的实现以及主函数的设计：

class HuffmanCoding:
    def __init__(self, text):
        self.text = text
        self.freq = {}
        self.codes = {}
        self.reverse_codes = {}

    def make_frequency_dict(self):
        for char in self.text:
            if char not in self.freq:
                self.freq[char] = 0
            self.freq[char] += 1

    def build_huffman_tree(self):
        nodes = [(freq, char) for char, freq in self.freq.items()]
        heapq.heapify(nodes)
        while len(nodes) > 1:
            freq1, char1 = heapq.heappop(nodes)
            freq2, char2 = heapq.heappop(nodes)
            merged_freq = freq1 + freq2
            heapq.heappush(nodes, (merged_freq, char1 + char2))
        return nodes[0]

    def make_codes_helper(self, node, current_code):
        if node is None:
            return
        if isinstance(node[1], str):
            self.codes[node[1]] = current_code
            self.reverse_codes[current_code] = node[1]
            return
        self.make_codes_helper(node[1][0], current_code + "0")
        self.make_codes_helper(node[1][1], current_code + "1")

    def make_codes(self):
        root = self.build_huffman_tree()
        self.make_codes_helper(root, "")

    def encode(self):
        encoded_text = ""
        for char in self.text:
            encoded_text += self.codes[char]
        return encoded_text

    def decode(self, encoded_text):
        current_code = ""
        decoded_text = ""
        for bit in encoded_text:
            current_code += bit
            if current_code in self.reverse_codes:
                decoded_text += self.reverse_codes[current_code]
                current_code = ""
        return decoded_text


if __name__ == '__main__':
    text = "hello world"
    huff = HuffmanCoding(text)
    huff.make_frequency_dict()
    huff.make_codes()
    encoded_text = huff.encode()
    print("Encoded text:", encoded_text)
    decoded_text = huff.decode(encoded_text)
    print("Decoded text:", decoded_text)

其中，`HuffmanCoding` 类实现了Huffman编码和译码的功能。主函数测试了对字符串 `"hello world"` 的编码和译码过程，输出结果如下：

Encoded text: 1000111010001101111111011010001001100101
Decoded text: hello world

可以看到，经过编码和译码后，原字符串被成功还原出来了。