哈夫曼树和哈夫曼编码

深藏阁楼爱情的钟 2023-03-12 12:15 8阅读 0赞

哈夫曼树和哈夫曼编码

#include <stdio.h>
    #include <string.h>
    #define N 50		//叶子结点数
    #define M 2*N-1		//树中结点总数
    typedef struct
    {
    	char data[5];	//结点值
    	double weight;	//权重
    	int parent;		//双亲结点
    	int lchild;		//左孩子结点
    	int rchild;		//右孩子结点
    } HTNode;
    typedef struct
    {
    	char cd[N];		//存放哈夫曼码
    	int start;
    } HCode;
    void CreateHT(HTNode ht[],int n)
    {
    	int i,k,lnode,rnode;
    	double min1,min2;
    	for (i=0;i<2*n-1;i++)			//所有结点的相关域置初值-1
    		ht[i].parent=ht[i].lchild=ht[i].rchild=-1;
    	for (i=n;i<2*n-1;i++)			//构造哈夫曼树
    	{
    		min1=min2=32767;			//lnode和rnode为最小权重的两个结点位置
    		lnode=rnode=-1;
    		for (k=0;k<=i-1;k++)
    			if (ht[k].parent==-1)	//只在尚未构造二叉树的结点中查找
    			{
    				if (ht[k].weight<min1)
    				{
    					min2=min1;rnode=lnode;
    					min1=ht[k].weight;lnode=k;
    				}
    				else if (ht[k].weight<min2)
    				{
    					min2=ht[k].weight;rnode=k;
    				}
    			}
    		ht[i].weight=ht[lnode].weight+ht[rnode].weight;
    		ht[i].lchild=lnode;ht[i].rchild=rnode;
    		ht[lnode].parent=i;ht[rnode].parent=i;
    	}
    }
    void CreateHCode(HTNode ht[],HCode hcd[],int n)
    {
    	int i,f,c;
    	HCode hc;
    	for (i=0;i<n;i++)	//根据哈夫曼树求哈夫曼编码
    	{
    		hc.start=n;c=i;
    		f=ht[i].parent;
    		while (f!=-1)	//循序直到树根结点
    		{
    			if (ht[f].lchild==c)	//处理左孩子结点
    				hc.cd[hc.start--]='0';
    			else					//处理右孩子结点
    				hc.cd[hc.start--]='1';
    			c=f;f=ht[f].parent;
    		}
    		hc.start++;		//start指向哈夫曼编码最开始字符
    		hcd[i]=hc;
    	}
    }
    void DispHCode(HTNode ht[],HCode hcd[],int n)
    {
    	int i,k;
    	double sum=0,m=0;
    	int j;
    	printf("  输出哈夫曼编码:\n"); //输出哈夫曼编码
    	for (i=0;i<n;i++)
    	{
    		j=0;
    		printf("      %s:\t",ht[i].data);
    		for (k=hcd[i].start;k<=n;k++)
    		{
    			printf("%c",hcd[i].cd[k]);
    			j++;
    		}
    		m+=ht[i].weight;
    		sum+=ht[i].weight*j;
    		printf("\n");
    	}
    	printf("\n  平均长度=%g\n",1.0*sum/m);
    }
    void main()
    {
    	int n=8,i;		//n表示初始字符串的个数
    	char *str[]={"a","b","c","d","e","f","g","h"};
    	double fnum[]={0.07,0.19,0.02,0.06,0.32,0.03,0.21,0.1};
    	HTNode ht[M];
    	HCode hcd[N];
    	for (i=0;i<n;i++)
    	{
    		strcpy(ht[i].data,str[i]);
    		ht[i].weight=fnum[i];
    	}
    	printf("\n");
    	CreateHT(ht,n);
    	CreateHCode(ht,hcd,n);
    	DispHCode(ht,hcd,n);
    	printf("\n");
    }