shannon编码

    最近老师硬是要交作业，所以出于无奈胡乱写写，还望各位不吝赐教。

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <iostream.h>
#include <string.h>

 

int num;   //输入的字符个数
int i,j;
float temp_p;  //过渡概率
char  temp_char[20];//过渡字符
char  code[200];    //编译出来的码字

struct shannon_code{
char  m_in[20];  //输入的字符
float m_p;   //输入的字符的概率 
float m_addp;  //累加概率
int m_length;       //需要的码长     
}shannon[30];

char *m_code;       //输出的码字

void sequence()  //按概率从大到小排序
{
 for (i=1;i<=num;i++)
 {
  for (int j=i+1;j<=num;j++)
  {
   if(shannon[j].m_p>=shannon[i].m_p)
   {
    temp_p=shannon[i].m_p;
    shannon[i].m_p=shannon[j].m_p;
    shannon[j].m_p=temp_p;
    strcpy(temp_char,shannon[i].m_in);
    strcpy(shannon[i].m_in,shannon[j].m_in);
    strcpy(shannon[j].m_in,temp_char);
   }
  }
 }
}

void code_length() //计算所需码长
{
 for (i=1;i<=num;i++)
 {
  int temp=(int)(log10(1.0/shannon[i].m_p)/log10(2));
  if (temp-log10(1.0/shannon[i].m_p)/log10(2)!=0)
  shannon[i].m_length=temp+1;
  else shannon[i].m_length=temp;
 }
}

void shannoncode() //进行香农编码
{
 float temp_addp; //过渡累加概率
 if(i==1)
  shannon[i].m_addp=0;
 else
  shannon[i].m_addp=shannon[i-1].m_addp+shannon[i-1].m_p;
  temp_addp=shannon[i].m_addp;
 for (j=0;j<shannon[i].m_length;j++)
 {
  temp_addp=temp_addp*2;
  if (temp_addp>=1)
  {
   code[j]=(int)temp_addp+48;
   temp_addp=temp_addp-1; 
  }
  else
   code[j]=(int)temp_addp+48;
 }
 code[shannon[i].m_length]='/0';
 
}

void main()
{
 cout<<"input the numbers of message(num<30):"<<endl;         //输入信源个数
 cin>>num;       
 cout<<"input the characters and their's probability:"<<endl; //输入各个信源的概率
 for (i=1;i<=num;i++)
 {
  cout<<"character"<<i<<":   ";
  cin>>shannon[i].m_in;
  cout<<"probability of character"<<i<<":   ";
  cin>>shannon[i].m_p;
 }
 sequence();              
 cout<<"After order from big to small by probability :"<<endl; //经过从大到小的排序后排列
 for (i=1;i<=num;i++)
 {
  cout<<shannon[i].m_in<<":  "<<shannon[i].m_p<<"   "<<endl;
 }
 code_length();             //输出各个信源编码所需要的码长
 cout<<"the length of each character: "<<endl;
 for (i=1;i<=num;i++)
 {
  cout<<shannon[i].m_in<<":   "<<shannon[i].m_length<<"   "<<endl;
 }
 cout<<"The code of character is:  "<<endl;      //各个信源编码后的码字
 for (i=1;i<=num;i++)
 {
  shannoncode();
  cout<<shannon[i].m_in<<":   ";
  for (j=0;j<shannon[i].m_length;j++)
   cout<<code[j];
  cout<<endl;
 }
 
}