#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <conio.h>
#pragma warning(disable:4996)
typedef struct HuffmanTree
{
int weight;//权值
int parent;//父节点
int left;//左子树
int right;//右子树
};
typedef char *HuffmanCode;//Huffmancode编码
//从1-x个节点选择parent节点为0，权重最小的两个节点
void SelectNode(HuffmanTree *ht, int n, int *bt1, int *bt2){
int i;
HuffmanTree *ht1, *ht2, *t;
ht1 = ht2 = NULL;//初始化两个节点为空
for (i = 1; i <= n; ++i)//循环处理1-n个节点（包括叶节点和非叶节点）
{
if (!ht[i].parent)//父节点为空(节点的parent为0)
{
if (ht1 == NULL)//节点指针1为空
{
ht1 = ht + i;//指向第i个节点
continue;//继续循环
}
if (ht2 == NULL)
{
ht2 = ht + i;
if (ht1->weight > ht2->weight)//比较两个值的权重，使ht1指向权值大的
{
t = ht2;
ht2 = ht1;
ht1 = t;
}
continue;//继续循环
}
if (ht1 && ht2)//若两个值都有效
{
if (ht[i].weight <= ht1->weight)//第i个节点权重小于ht1指向的节点
{
ht2 = ht1;//ht2保存ht1,因为这时ht1指向的节点成为第2小的
ht1 = ht + i;
}
else if (ht[i].weight < ht2->weight)//若第i个节点权重小于ht2指向的权重
{
ht2 = ht + i;
}
}
}
}
if (ht1 > ht2)//增加比较，使二叉树左侧为叶节点
{
*bt2 = ht1 - ht;
*bt1 = ht2 - ht;
}
else
{
*bt1 = ht1 - ht;
*bt2 = ht2 - ht;
}
}
void CreateTree(HuffmanTree *ht, int n, int *w){
int i, m = 2 * n - 1;//总的节点总数
int bt1, bt2;//二叉树节点序与
if (n <= 1)//只有一个节点就无法创建
{
return;
}
for (i = 0; i <= n; ++i)//初始化节点
{
ht[i].weight = w[i - 1];
ht[i].parent = 0;
ht[i].left = 0;
ht[i].right = 0;
}
for (; i <= m; ++i)//初始化后序节点
{
ht[i].weight = 0;
ht[i].parent = 0;
ht[i].left = 0;
ht[i].right = 0;
}
for (i = n + 1; i <= m; ++i)//逐个计算非叶节点，创建Huffman树
{
SelectNode(ht, i - 1, &bt1, &bt2);
ht[bt1].parent = i;
ht[bt2].parent = i;
ht[i].left = bt1;
ht[i].right = bt2;
ht[i].weight = ht[bt1].weight + ht[bt2].weight;
}
}
//
void HuffmanCoding(HuffmanTree *ht, int n, HuffmanCode *hc){
char *cd;
int start, i;
int current, parent;
cd = (char*)malloc(sizeof(char)*n);//用来临时存放一个字符编码的结果
cd[n - 1] = '\0';//设置字符串结束标志
for (i = 1; i <= n; i++)
{
start = n - 1;
current = i;
parent = ht[current].parent;//获取当前节点的父节点；
while (parent)
{
if (current == ht[parent].left)//若该节点的父节点是做左子树
{
cd[--start] = '0';//设置编码为0
}
else//若该节点是父节点的右子树
{
cd[--start] = '1';//设置编码为1
}
current = parent;//设置当前节点指向父节点
parent = ht[parent].parent;//获取当前节点的父节点序号；
}
hc[i - 1] = (char*)malloc(sizeof(char)*(n - start));
strcpy(hc[i - 1], &cd[start]);//复制生成生成的编码
}
free(cd);//释放编码占用的字符
}
void Encode(HuffmanCode *hc, char *alphabet, char *str, char *code){
//将一个字符串转换为Huffman编码
//hc为Huffman编码表，alphabet为对应的字母表，str为需要转换的字符串，code返回转换的结果
int len = 0, i = 0, j;
code[0] = '\0';
while (str[i])
{
j = 0;
while (alphabet[j] != str[i])
{
j++;
}
strcpy(code + len, hc[j]);//将对应字母的Huffman编码复制code指定位置
len = len + strlen(hc[j]);//累加字符串长度
i++;
}
code[len] = '\0';
}
void Decode(HuffmanTree *ht, int m, char *code, char *alphabet, char *decode){
//将一个huffman编码组成的字符串转换为明文字符串
//ht为huffman二叉树，m为字符数量，alphabet为对应的字母表，str需转换的字符串
int position = 0, i, j = 0;
m = 2 * m - 1;
while (code[position])//字符串未结束
{
for (i = m; ht[i].left && ht[i].right; position++)
{
if (code[position] == '0')//编码位为0
{
i = ht[i].left;
}
else
{
i = ht[i].right;//处理右子树
}
}
decode[j] = alphabet[i - 1];//得到一个字母
j++;//处理下一个字符
}
decode[j] = '\0';//字符串结尾
}
//主函数
int main(void){
int i, n = 4, m;
char test[] = "DBDACDADCCDBDCBADBCABABA";
char code[100], code1[100];
char alphabet[] = { 'A', 'B', 'C', 'D', };//四个字符
int w[] = { '5', '7', '2', '13' };//四个字符的权重
HuffmanTree *ht;
HuffmanCode *hc;
m = 2 * n - 1;
ht = (HuffmanTree *)malloc((m + 1)*sizeof(HuffmanTree));//申请内存，保存赫夫曼树
if (!ht)
{
printf("内存分配失败！");
exit(0);
}
hc = (HuffmanCode *)malloc(n*sizeof(char*));
if (!hc)
{
printf("分配内存失败！");
exit(0);
}
//创建赫夫曼树
CreateTree(ht, n, w);
HuffmanCoding(ht, n, hc);//根据赫夫曼树生成的赫夫曼编码
for (i = 1; i <= n; i++)
{
printf("字母：%c,权重：%d,编码为：%s\n", alphabet[i - 1], ht[i].weight, hc[i - 1]);
}
Encode(hc, alphabet, test, code);//根据赫夫曼编码生成编码字符串
printf("\n字符串：\n%s\n转换后为：\n%s\n", test, code);
Decode(ht, n, code, alphabet, code1);//根据编码字符串生成解码后的字符串
printf("\n编码：\n%s\n转换后为：\n%s\n", code, code1);
_getch();
return 0;
}
