赫夫曼树编码解码实例(C)

//HuffmanTree.h#include <stdlib.h>#include <stdio.h>#include <string.h>#define OVERFLOW -1typedef struct{    char data;           //节点所存字符    unsigned int weight;    //节点权重    unsigned int parent,lchild,rchild;}HTNode, *HuffmanTree;     //动态分配数组存储赫夫曼树typedef char** HuffmanCode;//动态分配数组存储赫夫曼编码表//从T的1到n个节点中找出没有结合（即parent=0）的节点中权重weight最小的两个节点的下标；用l，r带回；void Select(HuffmanTree T,int n,int&l,int&r){    HuffmanTree p=T+1;int a=0,b=0;    for(int i=1;i<=n;++i,++p){        if(!p->parent){//找出双亲节点为空的节点；            if(!a){l=i;a=1;}            else if(!b){r=i;b=1;}            else if(p->weight<(T+l)->weight||p->weight<(T+r)->weight){                if((T+l)->weight<=(T+r)->weight)r=i;                else l=i;            }        }    }}//w存放n个字符的权值(均>0)，构造赫夫曼树HT，并求出n个字符的赫夫曼编码HC//HT为赫夫曼树，HC为赫夫曼编码，w为权重数组，n为w长度void HuffmanCoding(HuffmanTree &HT, HuffmanCode &HC, int *w, char* c, int n){    if(n<=1) return;    int m = 2*n-1;    HT = (HuffmanTree)malloc((m+1)*sizeof(HTNode)); //0号单元未用    HuffmanTree p;    int i;    for(p=HT+1,i=1; i<=n; ++i,++p,++w) *p = {c[i-1],*w,0,0,0};    for(i=n+1; i<=m; ++i, ++p)         *p = {0,0,0,0,0};    for(i=n+1; i<=m; ++i){ //建赫夫曼树        //在HT[1..i-1]选择parent为0且weight最小的两个节点，其序号分别为s1和s2。        int s1,s2;        Select(HT, i-1, s1, 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;    }    //---从叶子到根逆向求每个字符的赫夫曼编码---    HC = (HuffmanCode)malloc((n+1)*sizeof(char *)); //分配n个字符编码的头指针向量    char* cd = (char *)malloc(n*sizeof(char));          //分配求编码的工作空间    cd[n-1] = '\0';    //编码结束符    for(i=1; i<=n; ++i){        //逐个字符求赫夫曼编码        int start = n-1;  //编码结束符位置        int c,f;        for(c=i, f=HT[i].parent; f!=0; c=f,f=HT[f].parent) //从叶子到根逆向求编码            if(HT[f].lchild == c) cd[--start] = '0';            else cd[--start] = '1';        HC[i] = (char *)malloc((n-start)*sizeof(char));  //为第i个字符编码分配空间        strcpy(HC[i],&cd[start]); //从cd复制编码(串)到HC    }    free(cd);  //释放工作空间}//输出赫夫曼编码//HC为赫夫曼编码，w为权重数组，n为w长度，c为字符数组void PrintHuffmanCode(HuffmanCode HC,int* w,char* c,int n){    char *p;    int i;    for(i=1;i<=n;++i){        printf("字符：%c，权重：%3d，编码：", c[i-1], w[i-1]);        p=HC[i];        printf("%s\n",p);    }}//返回某字符的赫夫曼编码//HC为赫夫曼编码，c为字符数组，n为c长度，ch为要编码的字符char* EnCode(HuffmanCode HC, char* c, char ch, int n){    int i;    for(i=0;i<n;++i){        if(c[i]==ch){            char *p = HC[i+1];            return p;        }    }}//解码//s为待解码字符串，HT为赫夫曼树char* DeCode(const char*s, HuffmanTree HT){    int i; HuffmanTree p=HT;    static char result[500];    int j=0;    //寻找根节点    while(p->parent!=0) p++;    const HuffmanTree root = p;    for(i=0; i<strlen(s); ++i){        if(s[i]=='0'){            if(p->lchild!=0){                p=HT+p->lchild;            }        }        else if(s[i]=='1'){            if(p->rchild!=0){                p=HT+p->rchild;            }        }        if(p->lchild==0&&p->rchild==0){            result[j]=p->data;++j;            p = root;        }    }    result[j] = '\0';    return result;}

#include "HuffmanTree.h"#include <stdio.h>int main(void){    char s[500];READ:    printf("请输入一段话：");    gets(s);    int i=0,w[1000]={0},*word; char *c; //word记录权值，c记录字符    while(s[i]!='\0'){ //出现次数计数        w[s[i]+500]++;        ++i;    }    int j=0; word = (int*)malloc(sizeof(int));             c = (char*)malloc(sizeof(char));    for(i=-500;i<500;++i){        if(w[i+500]!=0){            word = (int*)realloc(word,(j+1)*sizeof(int));            c = (char*)realloc(c,(j+1)*sizeof(char));            word[j] = w[i+500];            c[j] = i;            ++j;        }    }    const int len = j; //字符数组、权重数组长度    if(len==1){        printf("请输入大于1种字符！\n");        goto READ;    }    HuffmanCode HC;HuffmanTree HT;    HuffmanCoding(HT,HC,word,c,len);    PrintHuffmanCode(HC,word,c,len);    i=0;    printf("赫夫曼编码后结果为：");    char code[1000]={'\0'};    while(s[i]!='\0'){        strcat(code,EnCode(HC,c,s[i],len));        ++i;    }    printf("%s\n",code);    printf("解码结果为：%s",DeCode(code,HT));    printf("\n");    getchar();    return 0;}

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