哈夫曼编码贪心算法c++

以下是C++实现哈夫曼编码的贪心算法的示例代码：

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

// 定义哈夫曼树节点
struct HuffmanNode {
    char ch; // 字符
    int freq; // 频率
    HuffmanNode* left; // 左子节点
    HuffmanNode* right; // 右子节点
    HuffmanNode(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()(HuffmanNode* a, HuffmanNode* b) {
        return a->freq > b->freq;
    }
};

// 构建哈夫曼树
HuffmanNode* buildHuffmanTree(unordered_map<char, int>& freqMap) {
    priority_queue<HuffmanNode*, vector<HuffmanNode*>, cmp> 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('$', left->freq + right->freq);
        parent->left = left;
        parent->right = right;
        pq.push(parent);
    }
    return pq.top();
}

// 递归遍历哈夫曼树，生成编码表
void generateHuffmanCode(HuffmanNode* root, string code, unordered_map<char, string>& codeMap) {
    if (!root) {
        return;
    }
    if (root->ch != '$') {
        codeMap[root->ch] = code;
    }
    generateHuffmanCode(root->left, code + "0", codeMap);
    generateHuffmanCode(root->right, code + "1", codeMap);
}

// 哈夫曼编码
string huffmanEncode(string s) {
    unordered_map<char, int> freqMap;
    for (char c : s) {
        freqMap[c]++;
    }
    HuffmanNode* 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 huffmanDecode(string s, HuffmanNode* root) {
    string res = "";
    HuffmanNode* cur = root;
    for (char c : s) {
        if (c == '0') {
            cur = cur->left;
        } else {
            cur = cur->right;
        }
        if (cur->ch != '$') {
            res += cur->ch;
            cur = root;
        }
    }
    return res;
}

// 测试代码
int main() {
    string s = "abacabad";
    string encoded = huffmanEncode(s);
    cout << "Encoded string: " << encoded << endl;
    HuffmanNode* root = buildHuffmanTree({{'a', 2}, {'b', 2}, {'c', 1}, {'d', 1}});
    string decoded = huffmanDecode(encoded, root);
    cout << "Decoded string: " << decoded << endl;
    return 0;
}