哈夫曼编码实现的代码

哈夫曼编码是一种常用的数据压缩算法，它可以将一些出现频率较高的字符用较短的编码表示，从而达到压缩数据的目的。下面是一个简单的C++实现：

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

using namespace std;

// 定义哈夫曼树节点
struct HuffmanNode {
    char ch; // 字符
    int freq; // 频率
    HuffmanNode *left, *right; // 左右子节点

    HuffmanNode(char c, int f) : ch(c), freq(f), left(nullptr), right(nullptr) {}
};

// 定义哈夫曼树节点比较函数
struct Compare {
    bool operator()(HuffmanNode* a, HuffmanNode* b) {
        return a->freq > b->freq;
    }
};

// 构建哈夫曼树
HuffmanNode* buildHuffmanTree(const string& str) {
    // 统计字符频率
    unordered_map<char, int> freqMap;
    for (char c : str) {
        freqMap[c]++;
    }

    // 构建哈夫曼树
    priority_queue<HuffmanNode*, vector<HuffmanNode*>, Compare> pq;
    for (auto& p : freqMap) {
        pq.push(new HuffmanNode(p.first, p.second));
    }
    while (pq.size() > 1) {
        HuffmanNode* left = pq.top();
        pq.pop();
        HuffmanNode* right = pq.top();
        pq.pop();
        HuffmanNode* parent = new HuffmanNode('\0', left->freq + right->freq);
        parent->left = left;
        parent->right = right;
        pq.push(parent);
    }
    return pq.top();
}

// 生成哈夫曼编码表
void generateHuffmanCodeTable(HuffmanNode* root, string code, unordered_map<char, string>& codeTable) {
    if (!root) {
        return;
    }
    if (root->ch != '\0') {
        codeTable[root->ch] = code;
    }
    generateHuffmanCodeTable(root->left, code + "0", codeTable);
    generateHuffmanCodeTable(root->right, code + "1", codeTable);
}

// 哈夫曼编码
string huffmanEncode(const string& str) {
    // 构建哈夫曼树
    HuffmanNode* root = buildHuffmanTree(str);

    // 生成哈夫曼编码表
    unordered_map<char, string> codeTable;
    generateHuffmanCodeTable(root, "", codeTable);

    // 哈夫曼编码
    string encodedStr;
    for (char c : str) {
        encodedStr += codeTable[c];
    }

    return encodedStr;
}

// 哈夫曼解码
string huffmanDecode(const string& str, HuffmanNode* root) {
    string decodedStr;
    HuffmanNode* cur = root;
    for (char c : str) {
        if (c == '0') {
            cur = cur->left;
        } else {
            cur = cur->right;
        }
        if (cur->ch != '\0') {
            decodedStr += cur->ch;
            cur = root;
        }
    }
    return decodedStr;
}

int main() {
    string str = "hello world";
    string encodedStr = huffmanEncode(str);
    cout << "Encoded string: " << encodedStr << endl;

    HuffmanNode* root = buildHuffmanTree(str);
    string decodedStr = huffmanDecode(encodedStr, root);
    cout << "Decoded string: " << decodedStr << endl;

    return 0;
}