怎么编写哈夫曼树作为头文件

以下是一个简单的哈夫曼树头文件的示例：

#ifndef HUFFMAN_TREE_H
#define HUFFMAN_TREE_H

#include <iostream>
#include <queue>
#include <unordered_map>

class HuffmanNode {
public:
    char c;
    int freq;
    HuffmanNode* left;
    HuffmanNode* right;

    HuffmanNode(char c, int freq) {
        this->c = c;
        this->freq = freq;
        left = nullptr;
        right = nullptr;
    }

    bool is_leaf() {
        return (left == nullptr && right == nullptr);
    }

    static bool compare(HuffmanNode* a, HuffmanNode* b) {
        return a->freq > b->freq;
    }
};

class HuffmanTree {
public:
    HuffmanNode* root;

    HuffmanTree(std::unordered_map<char, int>& freq_map) {
        std::priority_queue<HuffmanNode*, std::vector<HuffmanNode*>, decltype(&HuffmanNode::compare)> pq(&HuffmanNode::compare);
        for (auto& p : freq_map) {
            pq.push(new HuffmanNode(p.first, p.second));
        }
        while (pq.size() > 1) {
            auto a = pq.top(); pq.pop();
            auto b = pq.top(); pq.pop();
            auto c = new HuffmanNode('\0', a->freq + b->freq);
            c->left = a;
            c->right = b;
            pq.push(c);
        }
        root = pq.top();
    }

    void encode(std::string& s, std::unordered_map<char, std::string>& encoding_map) {
        std::string code;
        encode_helper(root, code, encoding_map);
        std::string encoded;
        for (char c : s) {
            encoded += encoding_map[c];
        }
        s = encoded;
    }

    void decode(std::string& s) {
        std::string decoded;
        auto node = root;
        for (char c : s) {
            if (c == '0') {
                node = node->left;
            } else {
                node = node->right;
            }
            if (node->is_leaf()) {
                decoded += node->c;
                node = root;
            }
        }
        s = decoded;
    }

private:
    void encode_helper(HuffmanNode* node, std::string& code, std::unordered_map<char, std::string>& encoding_map) {
        if (node->is_leaf()) {
            encoding_map[node->c] = code;
            return;
        }
        code.push_back('0');
        encode_helper(node->left, code, encoding_map);
        code.pop_back();
        code.push_back('1');
        encode_helper(node->right, code, encoding_map);
        code.pop_back();
    }
};

#endif // HUFFMAN_TREE_H

该头文件包含两个类：`HuffmanNode` 和 `HuffmanTree`。

`HuffmanNode` 表示哈夫曼树中的一个节点，包含字符、频率以及左右子节点。

`HuffmanTree` 表示哈夫曼树，包含根节点以及编码和解码方法。

在 `HuffmanTree` 的构造函数中，使用优先队列来构建哈夫曼树。在编码和解码方法中，使用递归来遍历整个哈夫曼树，生成编码表和解码字符串。