Huffman编码相信学过数据结构这么课的都知道，概念也比较好理解，但是一般好理解的算法，在实际实现的过程中总是会遇到各种问题，一方面个人认为是对算法的实现过程不熟，另一方面在实际实现的过程中可以提升自己实现算法的能力，将自己的想法实现后还是比较满足的。下面是本人亲自实现的Huffman编码与解码的C语言实现，主要是记录一下自己当时的想法，供以后备忘吧。
数据结构定义如下：
typedef struct{
unsigned int weight;
unsigned int parent,lchild,rchild;
}HTNode, * HuffmanTree;
typedef char * * HuffmanCode;建树的关键代码如下：
//建立Huffman树，初始化1到n号元素的parent都为0，每次从parent为0的元素中
//挑选最小的两个建树之后,将它们的parent都置为对应号码
for(i = n + 1; i <= m; i++)
{
int min1, min2;
int j;
for(j = 1; j <= i - 1; j++)
if(HT[j].parent == 0) {min1 = j; break;}
for(j = 1; j <= i - 1; j++)
{
if(HT[j].parent != 0) continue;
if(HT[j].weight < HT[min1].weight)
min1 = j;
}
HT[min1].parent = i;
for(j = 1; j <= i - 1; j++)
if(HT[j].parent == 0) {min2 = j; break;}
for(j = 1; j <= i - 1; j++)
{
if(HT[j].parent != 0) continue;
if(HT[j].weight < HT[min2].weight)
min2 = j;
}
HT[min2].parent = i;
HT[i].lchild = min1;
HT[i].rchild = min2;
HT[i].weight = HT[min1].weight + HT[min2].weight;
}编码过程是更加树的结构，对每个非叶子节点的左子树为‘0’，右子树为‘1’。实现如下：
//编码
HuffmanCode HC = (HuffmanCode)malloc(n*sizeof(char *));
char * cd = (char *)malloc(n*sizeof(char));
cd[n-1] = ‘\0‘;
for(i = 0; i < n; i++)
{
int end = n - 1;
int cur = i + 1;
for (int a = HT[cur].parent; a != 0; cur = a, a = HT[a].parent)
{
if (HT[a].lchild == cur) cd[--end] = ‘0‘;
else if (HT[a].rchild == cur) cd[--end] = ‘1‘;
}
HC[i] = (char*)malloc((n-end)*sizeof(char));
strcpy(HC[i], &cd[end]);
}
free(cd);HuffmanCode HuffmanEncode(HuffmanTree & HT, unsigned int * w, int n)
{
int m = 2 * n - 1;
HT = (HuffmanTree)malloc((m+1)*sizeof(HTNode)); //第一个不用
int i;
for(i = 1; i <= n; i++)
{
HT[i].weight = w[i-1];
HT[i].parent = 0;
HT[i].lchild = 0;
HT[i].rchild = 0;
}
for(i = n + 1;i <= m; i++)
{
HT[i].weight = 0;
HT[i].parent = 0;
HT[i].lchild = 0;
HT[i].rchild = 0;
}
//建立Huffman树，初始化1到n号元素的parent都为0，每次从parent为0的元素中
//挑选最小的两个建树之后,将它们的parent都置为对应号码
for(i = n + 1; i <= m; i++)
{
int min1, min2;
int j;
for(j = 1; j <= i - 1; j++)
if(HT[j].parent == 0) {min1 = j; break;}
for(j = 1; j <= i - 1; j++)
{
if(HT[j].parent != 0) continue;
if(HT[j].weight < HT[min1].weight)
min1 = j;
}
HT[min1].parent = i;
for(j = 1; j <= i - 1; j++)
if(HT[j].parent == 0) {min2 = j; break;}
for(j = 1; j <= i - 1; j++)
{
if(HT[j].parent != 0) continue;
if(HT[j].weight < HT[min2].weight)
min2 = j;
}
HT[min2].parent = i;
HT[i].lchild = min1;
HT[i].rchild = min2;
HT[i].weight = HT[min1].weight + HT[min2].weight;
}
//编码
HuffmanCode HC = (HuffmanCode)malloc(n*sizeof(char *));
char * cd = (char *)malloc(n*sizeof(char));
cd[n-1] = ‘\0‘;
for(i = 0; i < n; i++)
{
int end = n - 1;
int cur = i + 1;
for (int a = HT[cur].parent; a != 0; cur = a, a = HT[a].parent)
{
if (HT[a].lchild == cur) cd[--end] = ‘0‘;
else if (HT[a].rchild == cur) cd[--end] = ‘1‘;
}
HC[i] = (char*)malloc((n-end)*sizeof(char));
strcpy(HC[i], &cd[end]);
}
free(cd);
return HC;
}对于编码后得到的编码字符序列HC，结果过程只需找到对应的下标即可。如下：
int HuffmanDecode(HuffmanTree HT,char* code, int n)
{
int i = 0, r;
for(int j = 1; j <= 2*n-1; j++)
if(HT[j].parent == 0) {r = j;break;}
while(code[i] == ‘0‘ || code[i] == ‘1‘)
{
if(code[i] == ‘0‘)
r = HT[r].lchild;
else if(code[i] == ‘1‘)
r = HT[r].rchild;
i++;
}
return r;
}int main()
{
printf("请输入待编码的字符个数：\n");
int n = 0;
scanf("%d", &n);
char codechar[n];
unsigned int weight[n];
printf("请输入编码字符：\n");
scanf("%s", codechar);
for(int i = 0; i < n; i++)
{
printf("\n请输入第%d个字符对应的权重：\n", i+1);
scanf("%d", &weight[i]);
}
HuffmanTree ht;
HuffmanCode hc = HuffmanEncode(ht, weight, n);
printf("\n构建的赫夫曼树如下（权重-左孩子-右孩子-父亲）：\n");
for(int i = 1; i <= 2*n-1; i++)
{
printf("%d\t%d\t%d\t%d\n", ht[i].weight, ht[i].lchild, ht[i].rchild, ht[i].parent);
}
printf("\n每个字符对应的编码如下:\n");
for(int i = 0; i < n; i++)
{
printf("%c\t:\t%s\n", codechar[i], hc[i]);
}
printf("\n请输入待解码的编码字符串：");
char str[n];
scanf("%s", str);
int hcindex = HuffmanDecode(ht, str, n);
printf("%s编码的字符是：%c\n", str, codechar[hcindex-1]);
return 0;
}
原文地址：http://blog.csdn.net/u010487568/article/details/24597659
