构造哈弗曼树

#include<iostream>
using namespace std;
struct HTreeNode{
	int weight;
	HTreeNode* parent;
	HTreeNode* lchild;
	HTreeNode* rchild;
};
HTreeNode* CreatHuffmanTree(int *w, int n)
{
	int m = 2 * n - 1;
	HTreeNode* HT = new HTreeNode[m];
	for (int i = 0; i < n; ++i){
		HT[i].weight = w[i]; HT[i].parent = HT[i].lchild = HT[i].rchild = NULL;
	}
	for (int i = n; i < m; ++i){
		HT[i].weight = 0; HT[i].parent = HT[i].lchild = HT[i].rchild = NULL;
	}
	int m1 = -1, m2;
	for (int i = n; i < m; ++i)
	{
		int m1 = -1, m2;
		for (int j = 0; j < i; ++j)
		{
			if (!HT[j].parent&&m1 == -1){ m1 = j; continue; }
			if (!HT[j].parent){ m2 = j; break; }
		}
		for (int j = m2; j < i; ++j)
		{
			if (!HT[j].parent)
			{
				if (HT[j].weight < HT[m1].weight){ m2 = m1; m1 = j; }
				else if (HT[j].weight < HT[m2].weight)m2 = j;
			}	
		}
		HT[i].weight = HT[m1].weight + HT[m2].weight;
		HT[i].lchild = &HT[m1]; HT[i].rchild = &HT[m2];
		HT[m1].parent = &HT[i]; HT[m2].parent = &HT[i];
	}
	return &HT[m - 1];
}
void PreOrderTraverse(HTreeNode* T)
{
	if (T)
	{
		cout << T->weight << " ";
		PreOrderTraverse(T->lchild);
		PreOrderTraverse(T->rchild);
	}
}
void main()
{
	int w[] = { 7, 5, 2, 4 };
	HTreeNode* HT = CreatHuffmanTree(w, sizeof(w) / sizeof(int));
	PreOrderTraverse(HT);
}