建立哈夫曼树,实现基于输入的字符及其权值求哈夫曼编码和进行编码解码的功能。要求:1.输出每个字符的哈夫曼编码。2.输入由上述若干字符组成的字符串,对电文进行编码并输出。3. 输入一串哈夫曼编码,进行解码并输出字符串。用C++写出代码

以下是C++实现的代码：

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

// 哈夫曼树节点
struct HuffmanNode {
    char ch;            // 当前节点存储的字符
    int freq;           // 当前节点存储的字符的频率
    HuffmanNode *left;  // 左子节点指针
    HuffmanNode *right; // 右子节点指针
    HuffmanNode(char _ch, int _freq) : ch(_ch), freq(_freq), left(nullptr), right(nullptr) {}
};

// 哈夫曼树比较器
struct HuffmanComparator {
    bool operator()(HuffmanNode *n1, HuffmanNode *n2) {
        return n1->freq > n2->freq;
    }
};

// 构造哈夫曼树
HuffmanNode *buildHuffmanTree(unordered_map<char, int> freqMap) {
    priority_queue<HuffmanNode *, vector<HuffmanNode *>, HuffmanComparator> pq;
    for (auto it : freqMap) {
        pq.push(new HuffmanNode(it.first, it.second));
    }
    while (pq.size() > 1) {
        auto left = pq.top();
        pq.pop();
        auto right = pq.top();
        pq.pop();
        auto parent = new HuffmanNode('\0', left->freq + right->freq);
        parent->left = left;
        parent->right = right;
        pq.push(parent);
    }
    return pq.top();
}

// 哈夫曼编码
void huffmanEncode(HuffmanNode *root, string str, unordered_map<char, string> &codeMap) {
    if (!root) {
        return;
    }
    if (!root->left && !root->right) {
        codeMap[root->ch] = str;
    }
    huffmanEncode(root->left, str + "0", codeMap);
    huffmanEncode(root->right, str + "1", codeMap);
}

// 哈夫曼编码压缩
string huffmanCompress(string str, unordered_map<char, string> &codeMap) {
    string compressed;
    for (char c : str) {
        compressed += codeMap[c];
    }
    return compressed;
}

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

int main() {
    string str = "hello world";
    unordered_map<char, int> freqMap;
    for (char c : str) {
        freqMap[c]++;
    }
    HuffmanNode *root = buildHuffmanTree(freqMap);
    unordered_map<char, string> codeMap;
    huffmanEncode(root, "", codeMap);
    for (auto it : codeMap) {
        cout << it.first << ": " << it.second << endl;
    }
    string compressed = huffmanCompress(str, codeMap);
    cout << "compressed: " << compressed << endl;
    string decoded = huffmanDecode(root, compressed);
    cout << "decoded: " << decoded << endl;
    return 0;
}

注意，本代码实现的哈夫曼编码和解码只支持ASCII字符集。如果需要支持更多字符集，需要对哈夫曼树节点的结构进行修改。