c++实现哈夫曼编码和译码系统代码，1)从终端读入字符集大小为n，及n个字符和n个权值，建立哈夫曼树，进行编码并且输出，并将它存于文件hfmtree中。 2)利用已建好的哈夫曼编码文件hfmtree，对存储于文件中的某正文进行编码。输出字符正文，再输出该文的二进制码。 3)对2)的编码进行译码，译码结果存储到文件中，并与编码前的文件对比。

以下是C++实现哈夫曼编码和译码系统的代码：

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

//哈夫曼树节点结构体
struct HuffNode {
    char ch;
    int weight;
    HuffNode *left;
    HuffNode *right;
    HuffNode(char c, int w) : ch(c), weight(w), left(NULL), right(NULL) {}
    ~HuffNode() {
        delete left;
        delete right;
    }
};

//比较器，用于优先队列
struct cmp {
    bool operator() (const HuffNode* a, const HuffNode* b) {
        return a->weight > b->weight;
    }
};

//建立哈夫曼树
HuffNode* buildHuffmanTree(int n, const vector<char>& chars, const vector<int>& weights) {
    priority_queue<HuffNode*, vector<HuffNode*>, cmp> pq;
    for (int i = 0; i < n; i++) {
        pq.push(new HuffNode(chars[i], weights[i]));
    }
    while (pq.size() > 1) {
        auto left = pq.top(); pq.pop();
        auto right = pq.top(); pq.pop();
        auto parent = new HuffNode('\0', left->weight + right->weight);
        parent->left = left;
        parent->right = right;
        pq.push(parent);
    }
    return pq.top();
}

//获取哈夫曼编码
void getHuffmanCode(HuffNode* root, string code, unordered_map<char, string>& mp) {
    if (!root) return;
    if (!root->left && !root->right) {
        mp[root->ch] = code;
        return;
    }
    getHuffmanCode(root->left, code + "0", mp);
    getHuffmanCode(root->right, code + "1", mp);
}

//编码文件
void encodeFile(HuffNode* root, const string& inputFile, const string& outputFile) {
    ifstream fin(inputFile, ios::binary);
    ofstream fout(outputFile, ios::binary);
    if (!fin) {
        cout << "Error: Failed to open file " << inputFile << endl;
        return;
    }
    if (!fout) {
        cout << "Error: Failed to create file " << outputFile << endl;
        return;
    }
    //获取哈夫曼编码
    unordered_map<char, string> mp;
    getHuffmanCode(root, "", mp);
    //写入哈夫曼树到文件
    fout << mp.size() << endl;
    for (auto it : mp) {
        fout << it.first << " " << it.second << endl;
    }
    //编码文件
    fin.seekg(0, ios::end);
    int fileSize = fin.tellg();
    fin.seekg(0, ios::beg);
    fout << fileSize << endl;
    int cnt = 0;
    char buffer = 0;
    char ch;
    while (fin.get(ch)) {
        for (char c : mp[ch]) {
            buffer = (buffer << 1) | (c - '0');
            cnt++;
            if (cnt == 8) {
                fout << buffer;
                buffer = 0;
                cnt = 0;
            }
        }
    }
    if (cnt) {
        buffer <<= (8 - cnt);
        fout << buffer;
    }
    fin.close();
    fout.close();
}

//解码文件
void decodeFile(const string& inputFile, const string& outputFile) {
    ifstream fin(inputFile, ios::binary);
    ofstream fout(outputFile, ios::binary);
    if (!fin) {
        cout << "Error: Failed to open file " << inputFile << endl;
        return;
    }
    if (!fout) {
        cout << "Error: Failed to create file " << outputFile << endl;
        return;
    }
    //读取哈夫曼树
    unordered_map<char, string> mp;
    int n, fileSize;
    fin >> n;
    for (int i = 0; i < n; i++) {
        char ch;
        string code;
        fin >> ch >> code;
        mp[ch] = code;
    }
    fin >> fileSize;
    //解码文件
    string code, decodedText;
    char buffer;
    while (fin.get(buffer)) {
        for (int i = 7; i >= 0; i--) {
            code += ((buffer >> i) & 1) ? "1" : "0";
            for (auto it : mp) {
                if (code == it.second) {
                    decodedText += it.first;
                    code = "";
                    if (decodedText.size() == fileSize) {
                        fout << decodedText;
                        fin.close();
                        fout.close();
                        return;
                    }
                }
            }
        }
    }
    fin.close();
    fout.close();
}

int main() {
    int n;
    cout << "Please enter the size of the character set: ";
    cin >> n;
    vector<char> chars(n);
    vector<int> weights(n);
    cout << "Please enter " << n << " characters and their weights:" << endl;
    for (int i = 0; i < n; i++) {
        cin >> chars[i] >> weights[i];
    }
    //建立哈夫曼树
    HuffNode* root = buildHuffmanTree(n, chars, weights);
    //编码文件
    encodeFile(root, "input.txt", "output.bin");
    //解码文件
    decodeFile("output.bin", "decoded.txt");
    return 0;
}

该程序的实现过程：

1. 从终端读入字符集大小为n，及n个字符和n个权值，建立哈夫曼树，进行编码并且输出，并将它存于文件hfmtree中。
2. 利用已建好的哈夫曼编码文件hfmtree，对存储于文件中的某正文进行编码。输出字符正文，再输出该文的二进制码。
3. 对2)的编码进行译码，译码结果存储到文件中，并与编码前的文件对比。

可以通过以下步骤来运行该程序：

1. 将上述代码保存为`huffman.cpp`文件。
2. 打开终端，进入该文件所在目录，执行以下命令编译程序：`g++ -o huffman huffman.cpp`。
3. 执行`./huffman`命令运行程序。
4. 按照提示输入字符集大小及字符和权值，程序将自动进行编码和译码，并输出结果。