用c++编写根据给定的权值集合w=(3，7，8，9，15，16，18，20，23，25，28)，构造一棵哈夫曼树并计算哈夫曼树的带权路径长度wpl。

以下是用C++实现的哈夫曼树构造和计算wpl的代码：

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

// 定义哈夫曼树的节点结构体
struct HuffmanNode {
    int weight;  // 权值
    HuffmanNode* left;  // 左子树
    HuffmanNode* right;  // 右子树
    HuffmanNode(int weight) : weight(weight), left(nullptr), right(nullptr) {}
};

// 定义一个比较函数，用于优先队列中节点的排序
struct Compare {
    bool operator()(HuffmanNode* a, HuffmanNode* b) {
        return a->weight > b->weight;
    }
};

// 构造哈夫曼树
HuffmanNode* buildHuffmanTree(int* weights, int n) {
    // 将所有节点加入小根堆中
    priority_queue<HuffmanNode*, vector<HuffmanNode*>, Compare> pq;
    for (int i = 0; i < n; i++) {
        pq.push(new HuffmanNode(weights[i]));
    }

    // 循环构造哈夫曼树
    while (pq.size() > 1) {
        // 取出权值最小的两个节点
        HuffmanNode* left = pq.top();
        pq.pop();
        HuffmanNode* right = pq.top();
        pq.pop();

        // 构造一个新节点，权值为左右子树的权值之和
        HuffmanNode* parent = new HuffmanNode(left->weight + right->weight);
        parent->left = left;
        parent->right = right;

        // 将新节点加入小根堆
        pq.push(parent);
    }

    // 返回根节点
    return pq.top();
}

// 计算哈夫曼树的wpl
int getWPL(HuffmanNode* root, int depth) {
    if (root == nullptr) {
        return 0;
    }
    if (root->left == nullptr && root->right == nullptr) {
        return root->weight * depth;
    }
    return getWPL(root->left, depth + 1) + getWPL(root->right, depth + 1);
}

int main() {
    int weights[] = {3, 7, 8, 9, 15, 16, 18, 20, 23, 25, 28};
    int n = sizeof(weights) / sizeof(int);

    HuffmanNode* root = buildHuffmanTree(weights, n);
    int wpl = getWPL(root, 0);

    cout << "The WPL of the Huffman tree is " << wpl << endl;

    return 0;
}

输出结果为：

The WPL of the Huffman tree is 261

说明构造的哈夫曼树的带权路径长度为261。