#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#define max_CL 10 /*maxsize of length of code*/
#define max_PN 9 /*输入序列的个数*/
typedef float datatype;
typedef struct SHNODE
{
datatype pb; /*第i个消息符号出现的概率*/
datatype p_sum; /*第i个消息符号累加概率*/
int kl; /*第i个消息符号对应的码长*/
int code[max_CL]; /*第i个消息符号的码字*/
struct SHNODE *next;
}shnolist;
datatype sym_arry[max_PN]; /*序列的概率*/
void pb_scan(); /*得到序列概率*/
void pb_sort(); /*序列概率排序*/
void valuelist(shnolist *L); /*计算累加概率，码长，码字*/
void codedisp(shnolist *L);void pb_scan()
{
int i;
datatype sum=0;
printf("input %d possible!\n",max_PN);
for(i=0;i<max_PN;i++)
{
printf(">>");
scanf("%f",&sym_arry[i]);
sum=sum+sym_arry[i];
}
/*判断序列的概率之和是否等于1，在实现这块模块时，scanf()对float数的缺陷，故只要满足0.99<sum<1.0001出现的误差是允许的*/
if(sum>1.0001||sum<0.99)
{
printf("sum=%f,sum must (<0.999<sum<1.0001)",sum);
pb_scan();
}
}
/*选择法排序*/
void pb_sort()
{
int i,j,pos;
datatype max;
for(i=0;i<max_PN-1;i++)
{
max=sym_arry[i];
pos=i;
for(j=i+1;j<max_PN;j++)
if(sym_arry[j]>max)
{
max=sym_arry[j];
pos=j;
}
sym_arry[pos]=sym_arry[i];
sym_arry[i]=max;
}
}
void codedisp(shnolist *L)
{
int i,j;
shnolist *p;
datatype hx=0,KL=0; /*hx存放序列的熵的结果，KL存放序列编码后的平均码字的结果*/
p=L->next;
printf("num\tgailv\tsum\t-lb(p(ai))\tlenth\tcode\n");
printf("\n");
for(i=0;i<max_PN;i++)
{
printf("a%d\t%1.3f\t%1.3f\t%f\t%d\t",i,p->pb,p->p_sum,-3.332*log10(p->pb),p->kl);
j=0;
for(j=0;j<p->kl;j++)
printf("%d",p->code[j]);
printf("\n");
hx=hx-p->pb*3.332*log10(p->pb); /*计算消息序列的熵*/
KL=KL+p->kl*p->pb; /*计算平均码字*/
p=p->next;
}
printf("H(x)=%f\tKL=%f\nR=%fbit/code",hx,KL,hx/KL); /*计算编码效率*/
}
shnolist *setnull()
{
shnolist *head;
head=(shnolist *)malloc(sizeof(shnolist));
head->next=NULL;
return(head);
}
shnolist *my_creat(datatype a[],int n)
{
shnolist *head,*p,*r;
int i;
head=setnull();
r=head;
for(i=0;i<n;i++)
{
p=(shnolist *)malloc(sizeof(shnolist));
p->pb=a[i];
p->next=NULL;
r->next=p;
r=p;
}
return(head);
}
void valuelist(shnolist *L)
{
shnolist *head,*p;
int j=0;
int i;
datatype temp,s;
head=L;
p=head->next;
temp=0;
while(j<max_PN)
{
p->p_sum=temp;
temp=temp+p->pb;
p->kl=-3.322*log10(p->pb)+1;
/*编码，*/
{
s=p->p_sum;
for(i=0;i<p->kl;i++)
p->code[i]=0;
for(i=0;i<p->kl;i++)
{
p->code[i]=2*s;
if(2*s>=1)
s=2*s-1;
else if(2*s==0)
break;
else s=2*s;
}
}
j++;
p=p->next;
}
}
int main(void)
{
shnolist *head;
pb_scan();
pb_sort();
head=my_creat(sym_arry,max_PN);
valuelist(head);
codedisp(head);
}
