请给出哈夫曼树的建树代码

以下是哈夫曼树的 C++ 代码：

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

// 哈夫曼树节点
struct HuffmanNode
{
    int weight;          // 权值
    int parent;          // 父节点下标
    int leftChild;       // 左子节点下标
    int rightChild;      // 右子节点下标
};

// 根据权值比较大小的仿函数
struct HuffmanCmp
{
    bool operator() (HuffmanNode a, HuffmanNode b)
    {
        return a.weight > b.weight;
    }
};

// 建立哈夫曼树
void BuildHuffmanTree(int* weight, int n, HuffmanNode* nodes)
{
    // 创建权值最小的优先队列
    priority_queue<HuffmanNode, vector<HuffmanNode>, HuffmanCmp> q;
    for(int i = 0; i < n; ++i)
    {
        nodes[i].weight = weight[i];
        nodes[i].parent = -1;
        nodes[i].leftChild = -1;
        nodes[i].rightChild = -1;
        q.push(nodes[i]);
    }
    
    // 构建哈夫曼树
    for(int i = 0; i < n-1; ++i)
    {
        // 取出权值最小的2个节点
        HuffmanNode node1 = q.top(); q.pop();
        HuffmanNode node2 = q.top(); q.pop();
        
        // 创建新节点，左右指针分别指向取出的2个节点
        HuffmanNode newNode = {node1.weight + node2.weight, -1, node1.weight < node2.weight ? node1 : node2, node1.weight < node2.weight ? node2 : node1};
        // 设置取出的2个节点的父节点指针
        node1.parent = i + n;
        node2.parent = i + n;
        // 将新节点加入队列
        q.push(newNode);
        
        // 新节点指向父节点
        nodes[i+n] = newNode;
    }
}

int main()
{
    int n = 5;
    int weight[5] = {5, 2, 4, 7, 1};
    HuffmanNode nodes[2*n-1];
    BuildHuffmanTree(weight, n, nodes);

    return 0;
}