#include"iostream"
#include<iomanip>
#include<string>
using namespace std;

struct HTNode
{
	int weight;													// 权值，设为整型
	int parent;													// 双亲位置
	int lchild;													// 左孩子位置
	int rchild;													// 右孩子位置
};


void select(HTNode* HT, int k, int& i1, int& i2)					// 在前K-1个结点中选择权值最小的两个根结点i和j
{
	int m1, m2;
	m1 = m2 = 32767; //
	i1 = i2 = 0;
	for (int j = 0; j < k; j++)
	{
		if (HT[j].weight < m1 && HT[j].parent == -1)
		{
			m2 = m1, i2 = i1;
			m1 = HT[j].weight;
			i1 = j;
		}
		else if (HT[j].weight < m2 && HT[j].parent == -1)
		{
			m2 = HT[j].weight;
			i2 = j;
		}
	}
}
// 算法5.16															// 构造哈夫曼树
void HuffmanTree(HTNode*& HT, int* w, int n)
{																	// n是叶子结点的个数，w是叶子结点的权值数组
	HTNode* p;
	int k, i;
	int i1, i2;
	p = HT;
	for (i = 0; i < 2 * n - 1; i++)
	{																// 设置初始状态，所有结点的指针为空
		HT[i].weight = 0;
		HT[i].parent = -1;
		HT[i].lchild = -1;
		HT[i].rchild = -1;
	}
	for (i = 0; i < n; i++)
	{																// 前n个结点的权值分别为个结点的权值
		HT[i].weight = w[i];
	}
	for (k = n; k < 2 * n - 1; k++)
	{																// 构造最优二叉树
		select(HT, k, i1, i2);											// 在前K-1个结点中选择权值最小的两个根结点i1和i2
		HT[i1].parent = k;
		HT[i2].parent = k;
		HT[k].weight = HT[i1].weight + HT[i2].weight;
		HT[k].lchild = i1;
		HT[k].rchild = i2;
	}
}


void DispHT(HTNode* HT, int n)										// 显示哈夫曼树存储	
{
	HTNode* p;
	p = HT;
	cout << "k" << setw(7) << "Weight" << setw(7) << "parent"
		<< setw(7) << "lchild" << setw(7) << "rchild" << endl;
	for (int k = 0; k < 2 * n - 1; k++)
	{
		cout << k << setw(7) << (p + k)->weight << setw(7) << (p + k)->parent
			<< setw(7) << (p + k)->lchild << setw(7) << (p + k)->rchild << endl;
	}
}

//算法5.17															// 构建哈夫曼编码
void CreateHFCode(HTNode* HT, int n, char** HC)
{
	int i, start, c, f;
	char* cd;
	cd = new char[n];
	cd[n - 1] = '\0';
	for (i = 0; i < n; i++)
	{
		start = n - 1;
		c = i;
		f = HT[i].parent;
		while (f != -1)
		{
			if (HT[f].lchild == c)
				cd[--start] = '0';
			else
				cd[--start] = '1';
			c = f; f = HT[f].parent;
		}
		cout << endl;
		HC[i] = new char[n - start];
		HC[i] = &cd[start];
		int j = 0;
		while (HC[i][j] != '\0')										// 显示编码
		{
			cout << HC[i][j];
			j++;
		}

	}
	delete cd;
	cout << endl;
}


int op;

int main()
{
	int* w;															// 权值数组
	int n;															// 权值个数
	int i;															// 工作变量
	HTNode* HT;														// 哈夫曼树
	char** HC;
	do
	{
		cout << "1-输入结点权值" << endl;
		cout << "2-生成最优二叉树" << endl;
		cout << "3-求哈夫曼编码" << endl;
		cout << "4-退出程序" << endl;
		cout << "请选择操作(1~4)：";
		cout << "\b\b";
		cin >> op;
		switch (op)
		{
		case 1:
			cout << "测试案例" << endl;
			cout << "7,5,2,3,5,6" << endl;
			cout << "请输入结点的个数：";
			cin >> n;
			w = new int[n];
			cout << "请依次输入权值：" << endl;
			for (i = 0; i < n; i++)
			{
				cout << "请输入第" << i + 1 << "个权值：";
				cin >> w[i];
			}
			break;
		case 2:
			HT = new HTNode[2 * n - 1];										// 申请最优二叉树存储空间
			HuffmanTree(HT, w, n);
			cout << "创建的哈夫曼树为：\n";
			DispHT(HT, n);
			system("pause");
			break;
		case 3:
			HC = new char* [n];											// 存储哈示曼编码
			cout << "哈夫曼编码为：\n";
			CreateHFCode(HT, n, HC);
			break;
		case 4:
			cout << "结束运行，Bye-Bye!" << endl;
			break;
		}
	} while (op != 4);
	return 0;
}