哈夫曼树
#include <stdio.h> #include <string.h>
#include <stdlib.h>
#include <malloc.h>
#include <conio.h>
typedef struct {
unsigned int weight;
unsigned int parent,lchild,rchild;
} HTNode,*HuffmanTree;
typedef char **HuffmanCode; /*用来存放哈夫曼编码*/
typedef struct {
unsigned int s1;
unsigned int s2;
} MinCode;
void Error(char *message);
HuffmanCode HuffmanCoding(HuffmanTree HT,HuffmanCode HC,unsigned int *w,unsigned int n);
MinCode Select(HuffmanTree HT,unsigned int n);
void Error(char *message)
{
fprintf(stderr,"Error:%s\n",message);
exit(1);
}
HuffmanCode HuffmanCoding(HuffmanTree HT,HuffmanCode HC,unsigned int *w,unsigned int n)
{ /*构造哈弗曼树ht,哈夫曼树的编码存放在hc中*/
unsigned int i,s1=0,s2=0;
HuffmanTree p;
char *cd;
unsigned int f,c,start,m;
MinCode min;
if(n<=1) Error("Code too small!");
m=2*n-1;
HT=(HuffmanTree)malloc((m+1)*sizeof(HTNode)); /*第0个单元未用*/
for(p=HT,i=0;i<=n;i++,p++,w++) /*初始化N个叶子结点*/
{
p->weight=*w;
p->parent=0;
p->lchild=0;
p->rchild=0;
}
for(;i<=m;i++,p++) /*将n-1个非叶子结点初始化为0*/
{
p->weight=0;
p->parent=0;
p->lchild=0;
p->rchild=0;
}
for(i=n+1;i<=m;i++)
{
min=Select(HT,i-1);
s1=min.s1;
s2=min.s2;
HT[s1].parent=i;
HT[s2].parent=i;
HT[i].lchild=s1;
HT[i].rchild=s2;
HT[i].weight=HT[s1].weight+HT[s2].weight;
}
printf("HT List:\n");
printf("Number\t\tweight\t\tparent\t\tlchild\t\trchild\n");
for(i=1;i<=m;i++)
printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\n",
i,HT[i].weight,HT[i].parent,HT[i].lchild,HT[i].rchild);
/*从叶子结点到根结点求每个字符的哈夫曼编码*/
HC=(HuffmanCode)malloc((n+1)*sizeof(char *));
cd=(char *)malloc(n*sizeof(char *)); /*为哈弗曼动态分配空间*/
cd[n-1]='\0';
for(i=1;i<=n;i++)
{
start=n-1;
for(c=i,f=HT[i].parent;f!=0;c=f,f=HT[f].parent)
if(HT[f].lchild==c) cd[--start]='0';
else cd[--start]='1';
HC[i]=(char *)malloc((n-start)*sizeof(char *));
strcpy(HC[i],&cd[start]);
}
free(cd);
return HC;
}
MinCode Select(HuffmanTree HT,unsigned int n)
{
unsigned int min,secmin;
unsigned int temp;
unsigned int i,s1,s2,tempi;
MinCode code;
s1=1;s2=1;
for(i=1;i<=n;i++)
if(HT[i].parent==0)
{
min=HT[i].weight;
s1=i;
break;
}
tempi=i++;
for(;i<=n;i++)
if(HT[i].weight<min&&HT[i].parent==0)
{
min=HT[i].weight;
s1=i;
}
for(i=tempi;i<=n;i++)
if(HT[i].parent==0&&i!=s1)
{
secmin=HT[i].weight;
s2=i;
break;
}
for(i=1;i<=n;i++)
if(HT[i].weight<secmin&&i!=s1&&HT[i].parent==0)
{
secmin=HT[i].weight;
s2=i;
}
if(s1>s2)
{
temp=s1;
s1=s2;
s2=temp;
}
code.s1=s1;
code.s2=s2;
return code;
}
void main()
{
HuffmanTree HT=NULL;
HuffmanCode HC=NULL;
unsigned int *w=NULL;
unsigned int i,n;
printf("Input n:\n");
scanf("%d",&n);
w=(unsigned int *)malloc((n+1)*sizeof(unsigned int *)); /*w为n个字符的权值*/
w[0]=0;
printf("Enter weight:\n");
for(i=1;i<=n;i++)
{
printf("w[%d]=",i);
scanf("%d",&w[i]);
}
HC=HuffmanCoding(HT,HC,w,n);
printf("HuffmanCode:\n");
printf("Number\t\tWeight\t\tCode\n");
for(i=1;i<=n;i++)
printf("%d\t\t%d\t\t%s\n",i,w[i],HC[i]);
}
谁帮我把这解释一下啊，这段代码看不懂啊！
