赫夫曼编码

根据哈夫曼编码的原理，编写一个程序，在用户输入结点权值的基础上求赫夫曼编码，并能把给定的编码进行译码。

（1）初始化：从键盘输入一字符串（或读入一文件），统计出现的字符和每个字符出现的频率，将字符出现的频率作为结点的权值，建立哈夫曼树。对各个字符进行哈夫曼编码，最后打印输出字符及每个字符对应的哈夫曼编码。 

（2）编码：利用已建好的哈夫曼树对“输入串”进行哈夫曼编码，最后打印输入串对应的哈夫曼编码（写入文件）。   √

（3）计算压缩比（选作）   

（4）译码：利用已建好的哈夫曼树对给定的一串代码进行译码，并打印输出得到的字符串。（选作）

测试数据：对字符串{casbcatbsatbat}进行编码；对电文“1101000”译码。字符集D={   ？},出现频率为w={？} 

//运行环境 VS2015#include "stdafx.h"#include "malloc.h"#include<stdio.h>#include<string.h>typedef struct HTNode{unsigned int weight;char parent;unsigned int lchild,   //count         rchild;}HTNode;typedef char * *HC;int Found(char c, HTNode ht[],int index){for (int i=1;i<index;i++){if (c == ht[i].parent)return i;}return 0;}void Select(HTNode ht[], int i, int&s1, int&s2) {int j, k = 1;while (ht[k].parent != 0)k++;s1 = k;for (j = 1; j <= i; ++j)  // Select the first least of ht[].weightif (ht[j].parent == 0 && ht[j].weight<ht[s1].weight)s1 = j;k = 1;while ((ht[k].parent != 0 || k == s1))k++;s2 = k;for (j = 1; j <= i; ++j)  // Select the second  least of ht[].weightif (ht[j].parent == 0 && ht[j].weight<ht[s2].weight&&j != s1)s2 = j;}int Aver(int n){int i = 0;int m = 1;for (;m < n;i ++){m *= 2;}return i;}#pragma warning(disable:4996)void main(){char st[101];  //字符种类字符串char ch[101];  //输入的所有字符字符串int num = 0;float haver=0; //赫夫曼编码平均字符编码长度HTNode *ht=(HTNode*)malloc(101*sizeof(HTNode));ht[0].lchild = 0;ht[0].parent = 1;while (char c = getchar()){if (c == '\n')break;ch[num] = c;num++;int temp = Found(c, ht, ht[0].parent);if (!temp){ht[ht[0].parent].lchild = 1;ht[ht[0].parent].parent = c;st[ht[0].parent] = c;ht[0].parent++;}else{ht[temp].lchild++;}ht[0].lchild++;}ch[num] = '\0';for (int i = 1;i < ht[0].parent;i++){ht[i].weight = (int)(((float)ht[i].lchild / (float)ht[0].lchild)*100);}int n = ht[0].parent - 1;    //字母种类总数int m = 2 * n - 1;for (int i = 1;i <= n;i++)ht[i] = { ht[i].weight,0,0,0 };for (int i = n + 1;i <= m;i++)ht[i] = { 0,0,0,0 };for (int i = n + 1;i <= m;++i){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;}HC hc = (HC)malloc((n + 1) * sizeof(char*));char *cd = (char*)malloc(n * sizeof(char));cd[n - 1] = '\0';for (int i = 1;i <= n;++i){int start = n - 1;int c;char f;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]);haver += (float)(ht[i].weight *strlen(hc[i])) / 100;}free(cd);FILE *fp;fp = fopen("d:\\code.txt", "w");for (num = 0;ch[num] != '\0';num++)   //遍历输入的字符{for (int j = 1;j <= n;j++)     //遍历编码表{if (ch[num] == st[j]){fprintf(fp, "%s",hc[j]);printf("%s", hc[j]);break;}}}fclose(fp);putchar('\n');printf("********译码表*********\n");for (int i = 1;i<=n;i++){printf("%c:%s\n", st[i],hc[i]);}printf("***********************\n");printf("赫夫曼编码平均码长=%0.2f\n", haver);printf("等长编码平均码长=%d\n", Aver(n));printf("赫夫曼编码的压缩率为%%%0.1lf\n",100.00-haver/(float)Aver(n)*100);printf("*********译码器********\n");printf("请输入要翻译的编码\n");char buffer[101]; //缓冲数组int index = 0;while (char c = getchar()){if (c == '\n')break;buffer[index] = c;      //将c存入缓冲index++;buffer[index] = '\0';for (int i = 1;i<=n;i++)            //遍历密钥表列{bool found = true;for (int j = 0;hc[i][j] != '\0';j++)  //遍历密钥表行{    if (buffer[j] != hc[i][j])    {        found = false;    break;    }    }    if (found)    {    printf("%c", st[i]);    index = 0;    break;    }}}}