求哈弗曼编码

/********************************************************
**         功能：求哈夫曼编码                          **
**         时间：2015年5月10号                         **
********************************************************/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAXLEN 10000
#define MAXVALUE 10000

//结构体形式的字符包含的信息
struct ChNode
{
    int ascii;//存储字符的asci码
    char ch;//存储字符
    int count;//字符出现的次数
};

//定义哈夫曼树节点的结构体
typedef struct HTNode
{
    int weight;
    int parent,lchild,rchild;
}HTNode;

typedef char * *HuffmanCode;//定义指针类型的数据类型HuffmanCode
typedef struct ChNode ChNode;//定义数据类型ChNode

void Count_Times(char text[],ChNode freq[]);
void Select(HTNode HT[],int i,int &s1,int &s2);
void HuffmanCoding(HTNode HT[],HuffmanCode &HC,ChNode freq[],char text[]);

void main()
{
    ChNode freq[256];//存储字符出现次数的数组
    char text[MAXLEN];//将字符存储到数组中以后反编译时用
    HTNode HT[511];
    HuffmanCode HC;
    
    Count_Times(text,freq);
    HuffmanCoding(HT,HC,freq,text);
}
void Count_Times(char text[],ChNode freq[])
{
    FILE *fp;//文件指针
    char chtmp;//临时存储从文件中读取的字符
    
    //跟freq数组赋初值
    for(int i=0;i<256;i++)
    {
        freq[i].ascii=i;
        freq[i].ch=(char)i;//强制转换为ascii码对应的字符型
        freq[i].count=0;
    }
    
    i=0;
    fp=fopen("a.txt","r");//以读的方式打开文件
    
    //统计文件里的字符的出现次数并赋值给text
    fscanf(fp,"%c",&chtmp);
    while(!feof(fp))
    {
        freq[chtmp].count++;
        fscanf(fp,"%c",&chtmp);
        text[i++]=chtmp;
        
    }
    fclose(fp);
    
    //以写方式打开文件并将统计结果输出到文件中
    fp=fopen("freq.txt","w");
    for(i=0;i<256;i++)
        fprintf(fp,"%d   %c   %d\n",freq[i].ascii,freq[i].ch,freq[i].count);
    fclose(fp);
    
}

//选出两个权值最小的结点
void Select(HTNode HT[],int i,int &s1,int &s2)
{
    int m1,m2;//用来存储最小的两个权值
    
    m1 = m2 = MAXVALUE;
    s1 = s2 = -1;//用来存储最小权值的字符的序号
    
    for(int j = 0;j <= i;j ++)
    {
        //若一个字符的权值小于m1且parent为空（没有已经用过）
        if(HT[j].weight > 0 && HT[j].weight < m1 && HT[j].parent == -1)//s1存储的是字符中权值最小的序号
        {
            //权值比s1小，将s1赋值给s2再将字符序号给s1
            m2 = m1;
            s2 = s1;
            m1 = HT[j].weight;
            s1 = j;
        }
        else if(HT[j].weight > 0 && HT[j].weight < m2 && HT[j].parent == -1)//s2存储的是字符中权值第二小的序号
        {
            m2 = HT[j].weight;
            s2 = j;

        }
    }
    
    
}

void HuffmanCoding(HTNode HT[],HuffmanCode &HC,ChNode freq[],char text[])
{
    //前256个单位有可能出现的字符将权值赋初值
    for(int i = 0;i < 256;i ++)
    {
        HT[i].weight = freq[i].count;
        HT[i].parent = -1;
        HT[i].lchild = -1;
        HT[i].rchild = -1;
    }
    //后面255的赋初值
    for(i = 256;i < 511;i ++)
    {
        HT[i].weight = 0;
        HT[i].parent = -1;
        HT[i].lchild = -1;
        HT[i].rchild = -1;
    }

    int s1,s2;

    //构造哈夫曼树的开始，构造parent节点
    for(i = 256;i < 511;i++)
    {
        Select(HT,i - 1,s1,s2);
        if(s1 != -1 && s2 != -1)
        {
            HT[i].weight = HT[s1].weight + HT[s2].weight;
            HT[s1].parent = i;
            HT[s2].parent = i;
            HT[i].lchild = s1;
            HT[i].rchild = s2;
        }
        else
        {
            HT[i - 1].parent = -1;
            break;
        }
    }

    //HuffmanTree.txt文件用来存放各个字符的权值、父母、孩子等信息
    FILE *fp;
    fp = fopen("HuffmanTree.txt","w");
    for(i = 0;i < 511;i ++)
        fprintf(fp,"(%d)    %d    %d    %d    %d\n",i,HT[i].weight,HT[i].parent,HT[i].lchild,HT[i].rchild);
    fclose(fp);

    //HC相当于一个存放指针类型的数组，每一个元素相对应于一个字符编码数组的首地址
    HC = (HuffmanCode)malloc(256 * sizeof(char *));
    char cd[256];
    cd[255] = '\0';
    int c,f;
    int start;
    for(i =0 ;i < 256;i ++)
    {
        if(HT[i].parent != -1)
        {
            start = 255;
            //记录每个字符的编码，是0还是1
            for(c = i;f = HT[c].parent,f != -1;c = f,f = HT[f].parent)
            {
                if(HT[f].lchild == c)
                    cd[--start] = '0';
                else
                    cd[--start] = '1';
            }
            HC[i] = (char *)malloc((256 - start) * sizeof(char));
            strcpy(HC[i],&cd[start]);
        }
        else
        {
            HC[i] = NULL;
        }
    }

    //HuffmanCode.txt文件中记录字符出现的次数及其哈弗曼编码
    fp = fopen("HuffmanCode.txt","w");
    fprintf(fp,"ASCII值\t字符\t出现次数\t编码 \n");
    for(i = 0;i < 256;i ++)
        if(HC[i] != NULL)
            fprintf(fp,"%d\t%c\t%d\t%s\n",i,i,freq[i]);
        fclose(fp);

        //以对应的哈弗曼编码形式输出到文件中去
        fp = fopen("translate.txt","w");
        char ch;
        i =0;
        while(text[i] != '\0')
        {
            ch = text[i ++];
            fprintf(fp,"%s",HC[ch]);
        }
        fclose(fp);

}