哈夫曼编码用c++实现

以下是C++实现哈夫曼编码的示例代码：

#include <iostream>
#include <queue>
#include <vector>
#include <string>
#include <unordered_map>
using namespace std;

// 定义哈夫曼树节点
struct TreeNode {
    char ch;
    int freq;
    TreeNode* left;
    TreeNode* right;
    TreeNode(char c, int f) : ch(c), freq(f), left(nullptr), right(nullptr) {}
};

// 定义比较函数，用于优先队列
struct cmp {
    bool operator()(TreeNode* a, TreeNode* b) {
        return a->freq > b->freq;
    }
};

// 构建哈夫曼树
TreeNode* buildHuffmanTree(unordered_map<char, int>& freqMap) {
    priority_queue<TreeNode*, vector<TreeNode*>, cmp> pq;
    for (auto& p : freqMap) {
        pq.push(new TreeNode(p.first, p.second));
    }
    while (pq.size() > 1) {
        TreeNode* left = pq.top();
        pq.pop();
        TreeNode* right = pq.top();
        pq.pop();
        TreeNode* parent = new TreeNode('#', left->freq + right->freq);
        parent->left = left;
        parent->right = right;
        pq.push(parent);
    }
    return pq.top();
}

// 递归生成哈夫曼编码
void generateHuffmanCode(TreeNode* root, string code, unordered_map<char, string>& codeMap) {
    if (!root) {
        return;
    }
    if (!root->left && !root->right) {
        codeMap[root->ch] = code;
    }
    generateHuffmanCode(root->left, code + "0", codeMap);
    generateHuffmanCode(root->right, code + "1", codeMap);
}

// 哈夫曼编码
string huffmanEncoding(string s) {
    unordered_map<char, int> freqMap;
    for (char c : s) {
        freqMap[c]++;
    }
    TreeNode* root = buildHuffmanTree(freqMap);
    unordered_map<char, string> codeMap;
    generateHuffmanCode(root, "", codeMap);
    string res = "";    for (char c : s) {
        res += codeMap[c];
    }
    return res;
}

// 哈夫曼解码
string huffmanDecoding(string s, TreeNode* root) {
    string res = "";
    TreeNode* cur = root;
    for (char c : s) {
        if (c == '0') {
            cur = cur->left;
        } else {
            cur = cur->right;
        }
        if (!cur->left && !cur->right) {
            res += cur->ch;
            cur = root;
        }
    }
    return res;
}

int main() {
    string s = "hello world";
    string encoded = huffmanEncoding(s);
    cout << "Encoded string: " << encoded << endl;
    TreeNode* root = buildHuffmanTree(unordered_map<char, int>());
    string decoded = huffmanDecoding(encoded, root);
    cout << "Decoded string: " << decoded << endl;
    return 0;
}