#include <iostream.h>
#include <stdlib.h>
const int MaxValue=10000;
const int MaxN = 10;
struct HaffNode
//哈夫曼樹的結點結構
{
	char x;
	int weight;								//權值
	int flag;								//標記
	int parent;								//雙親結點下標
	int leftChild;							//左孩子下標
	int rightChild;							//右孩子下標
};

struct Code
//存放哈夫曼編碼的數據元素結構
{
	char bit[MaxN];							//數組
	int start;								//編碼的起始下標
	int weight;	                            //字符的權值
	char x;
};
//建立葉結點個數為n權值為weight的哈夫曼樹haffTree

void Haffman(int n, HaffNode haffTree[])
{
	int j, m1, m2, x1, x2,i;//構造哈夫曼樹haffTree的n-1個非葉結點
	for(i = 0;i < n-1;i++)
	{
		m1 = m2 = MaxValue;
		x1 = x2 = 0;
		for(j = 0; j < n+i;j++)
		{
			if(haffTree[j].weight < m1 && haffTree[j].flag == 0)
			{
				m2 = m1;
				x2 = x1;
				m1 = haffTree[j].weight;
				x1 = j;
			}
			else if(haffTree[j].weight < m2 && haffTree[j].flag == 0)
			{
				m2 = haffTree[j].weight;
				x2 = j;
			}
		}		//將找出的兩棵權值最小的子樹合并為一棵子樹
		haffTree[x1].parent  = n+i;   
		haffTree[x2].parent  = n+i;
		haffTree[x1].flag    = 1;
		haffTree[x2].flag    = 1;
		haffTree[n+i].weight = haffTree[x1].weight+haffTree[x2].weight;
		haffTree[n+i].leftChild = x1;
		haffTree[n+i].rightChild = x2;
	}
	cout<<"構造完成。"<<endl;
}
void HaffmanCode(HaffNode haffTree[], int n, Code haffCode[])
//由n個結點的哈夫曼樹haffTree構造哈夫曼編碼haffCode
{
	Code *cd = new Code;
	int child, parent;
	int j,i;	
	//求n個葉結點的哈夫曼編碼
	for(i = 0; i < n; i++)		
	{
		cd->start = n-1;		//不等長編碼的最后一位為n-1
		cd->x=haffTree[i].x;
		cd->weight = haffTree[i].weight;	//取得編碼對應權值的字符
		child = i;
		parent = haffTree[child].parent;		//由葉結點向上直到根結點
		while(parent != 0)
		{
			if(haffTree[parent].leftChild == child)
				cd->bit[cd->start] = '0';				//左孩子結點編碼0
			else							
				cd->bit[cd->start] = '1';				//右孩子結點編碼1
			cd->start--;
			child = parent;
			parent = haffTree[child].parent;
		}
		
		//保存葉結點的編碼和不等長編碼的起始位
		for(j = cd->start+1; j < n; j++) 
			haffCode[i].bit[j]=cd->bit[j];
		haffCode[i].start  = cd->start;
		haffCode[i].weight = cd->weight;//記住編碼對應權值的字符
		haffCode[i].x=cd->x;
	}
	for(i = 0; i < n; i++)
	{
		cout <<"字符為："<<haffCode[i].x<<" "<< "Weight = " << haffCode[i].weight << "   Code = ";
		for(j = haffCode[i].start+1; j < n; j++)
			cout << haffCode[i].bit[j];
		cout << endl;
	}
	cout<<"編碼成功。"<<endl;
}
HaffNode *creat(int &n)
{
	HaffNode *haffTree = new HaffNode[2*n+1];
	int i=0;
	cout<<"請輸入"<<n<<"個字符：";
	for(i=0;i<n;i++)
		cin>>haffTree[i].x;
	cout<<"請輸入對應的權值:";
	
	//哈夫曼樹haffTree初始化。n個葉結點的哈夫曼樹共有2n-1個結點
	for(i=0; i < 2 * n - 1 ; i++)
	{
		if(i<n)
			cin>>haffTree[i].weight;
		else
			haffTree[i].weight = 0;
		haffTree[i].parent = 0;
		haffTree[i].flag   = 0;
		haffTree[i].leftChild = -1;
		haffTree[i].rightChild = -1;
	}
	return haffTree;
}
void deHaffmanCode(int n,Code haffCode[])
{
	char f[10];
	cout<<"請輸入碼字：";
	cin>>f;
	int i,j,m,b=0;
	for(i=0;i<n;i++)
	{
		j=haffCode[i].start+1;
		for(m=0;j<n;m++,j++)
			if(haffCode[i].bit[j]!=f[m])
				break;
			if(j>=n&&f[m]=='\0')			
			{
				b++;
				cout <<"字符為："<<haffCode[i].x<<" "<< "Weight = " << haffCode[i].weight<<endl;
			}			
	}
	if(b==0)
		cout<<"不存在這樣的碼字。請重新輸入！"<<endl;
}
int main()
{
	int i=0,n;
	HaffNode *myHaffTree;
	Code *myHaffCode;
	while(i!=5)
	{
		cout<<"--------1.輸入數據。"<<endl;
		cout<<"--------2.構造赫夫曼樹。"<<endl;
		cout<<"--------3.構造赫夫曼編碼。"<<endl;
		cout<<"--------4.譯碼。"<<endl;
		cout<<"--------5.退出。"<<endl;
		cout<<"請選擇:"<<endl;
		cin>>i;
		switch(i)
		{
		case 1:
			cout<<"請輸入數據的個數：";
			cin>>n;
			myHaffTree = new HaffNode[2*n+1];
			myHaffTree=creat(n);
			myHaffCode = new Code[n];
			break;
		case 2:
			Haffman(n, myHaffTree);
			break;
		case 3:
			HaffmanCode(myHaffTree,n,myHaffCode);
			break;
		case 4:
			deHaffmanCode(n,myHaffCode);
			break;
		case 5:
			break;
		default:
			break;
		}		
	}	
	return 0;	
}