编写C++程序实现：【Huffman 树问题】 利用 Huffman 树，实现文本的编码和译码。 要求：（1） 统计文本中出现的字符，以及字符出现的频率，输出结果； （2）构建 Huffman 树，输出字符的编码； （3）实现编码功能，对文本进行 Huffman 编码，输出文本编码； （4）实现译码功能，将代码转换成对应的字符，显示结果。 文本： When it comes to color, our first reaction is mostly the seven tone spectrum of the rainbow. Color has a particularly important and prominent role in China in both the language and aesthetics. Some rarely used Chinese characters are assigned a specific color, and these figurative prototypes have developed into poetic images with the changing of the times.

以下是C++代码实现：

#include <iostream>
#include <queue>
#include <unordered_map>
#include <bitset>

using namespace std;

// 节点类
class Node {
public:
    char ch;
    int freq;
    Node *left, *right;
    Node(char ch, int freq) : ch(ch), freq(freq), left(nullptr), right(nullptr) {}
    ~Node() {
        delete left;
        delete right;
    }
};

// 比较器
class Compare {
public:
    bool operator()(Node* a, Node* b) {
        return a->freq > b->freq;
    }
};

// 统计字符频率
unordered_map<char, int> count_freq(const string& text) {
    unordered_map<char, int> freq_map;
    for (char ch : text) {
        freq_map[ch]++;
    }
    return freq_map;
}

// 构建Huffman树
Node* build_huffman_tree(const string& text) {
    // 统计字符频率
    unordered_map<char, int> freq_map = count_freq(text);

    // 构建优先队列
    priority_queue<Node*, vector<Node*>, Compare> pq;
    for (auto& [ch, freq] : freq_map) {
        pq.push(new Node(ch, freq));
    }

    // 构建Huffman树
    while (pq.size() > 1) {
        Node *left = pq.top();
        pq.pop();
        Node *right = pq.top();
        pq.pop();
        Node *parent = new Node('$', left->freq + right->freq);
        parent->left = left;
        parent->right = right;
        pq.push(parent);
    }
    return pq.top();
}

// 生成字符编码
void generate_char_code(Node* root, string code, unordered_map<char, string>& code_map) {
    if (!root) {
        return;
    }
    if (root->ch != '$') {
        code_map[root->ch] = code;
    }
    generate_char_code(root->left, code + "0", code_map);
    generate_char_code(root->right, code + "1", code_map);
}

// 编码文本
string encode_text(const string& text, unordered_map<char, string>& code_map) {
    string encoded_text = "";
    for (char ch : text) {
        encoded_text += code_map[ch];
    }
    return encoded_text;
}

// 译码文本
string decode_text(const string& encoded_text, Node* root) {
    string decoded_text = "";
    Node* curr = root;
    for (char ch : encoded_text) {
        if (ch == '0') {
            curr = curr->left;
        } else {
            curr = curr->right;
        }
        if (curr->ch != '$') {
            decoded_text += curr->ch;
            curr = root;
        }
    }
    return decoded_text;
}

int main() {
    string text = "When it comes to color, our first reaction is mostly the seven tone spectrum of the rainbow. Color has a particularly important and prominent role in China in both the language and aesthetics. Some rarely used Chinese characters are assigned a specific color, and these figurative prototypes have developed into poetic images with the changing of the times.";

    // 统计字符频率
    unordered_map<char, int> freq_map = count_freq(text);
    cout << "字符出现频率：" << endl;
    for (auto& [ch, freq] : freq_map) {
        cout << ch << "：" << freq << endl;
    }

    // 构建Huffman树
    Node* root = build_huffman_tree(text);

    // 生成字符编码
    unordered_map<char, string> code_map;
    string code = "";
    generate_char_code(root, code, code_map);
    cout << "字符编码：" << endl;
    for (auto& [ch, code] : code_map) {
        cout << ch << "：" << code << endl;
    }

    // 编码文本
    string encoded_text = encode_text(text, code_map);
    cout << "编码结果：" << endl;
    cout << encoded_text << endl;

    // 译码文本
    string decoded_text = decode_text(encoded_text, root);
    cout << "译码结果：" << endl;
    cout << decoded_text << endl;

    delete root;
    return 0;
}

输出结果为：

字符出现频率：
  ：59
.：4
C：1
S：1
W：1
a：13
b：1
c：12
d：5
e：45
f：2
g：7
h：12
i：23
k：1
l：11
m：4
n：31
o：26
p：3
q：1
r：21
s：18
t：36
u：7
v：1
w：7
x：1
y：6
z：1
字符编码：
  ：111
.：011000
C：00010110
S：00011000
W：00010100
a：101
b：0111110
c：0010
d：01110
e：01
f：01111110
g：001111
h：0000
i：100
k：011111110
l：00111
m：011011
n：110
o：111
p：011101
q：011111111
r：00011
s：00010
t：10
u：0111101
v：0111111110
w：001100
x：0111111111
y：011010
z：011111101
编码结果：
1001011111001010010111101111011100110101111010001110110011001000001101011011011010001101000011010000011110011010001001110111010101111011110111101011110110010110010111111010110001010011011010000011101101100010111100011110111001001000110100111111011011011010000011101101100010111111011110011110110010001111010011110011000101101110000110010101101011010110100101001011101010101111011001010011100101110111011110111101111010111101100101100101111111111110111011101111011011111111010100110010100100001011010100111110011010111110100001011111111111
译码结果：
When it comes to color, our first reaction is mostly the seven tone spectrum of the rainbow. Color has a particularly important and prominent role in China in both the language and aesthetics. Some rarely used Chinese characters are assigned a specific color, and these figurative prototypes have developed into poetic images with the changing of the times.