哈夫曼树

#include <stdio.h>
#include <limits.h>
#include <string.h>
#include <stdlib.h>

#define N 6

typedef struct huffNode
{
unsigned int weight; //权重
unsigned int lchild, rchild, parent; //左右子节点和父节点
}HTNode, *HuffTree;
typedef char **HuffCode;

//找出数组中无父节点且权值最小的两个节点下标,分别用s1和s2保存
void select(const HuffTree &HT, int n, int &s1, int &s2);
//HT:哈夫曼树，HC:哈夫曼编码，w:构造哈夫曼树节点的权值，n:构造哈夫曼树节点的个数
void HuffmanCode(HuffTree &HT, HuffCode &HC, int *w, int n);

int main()
{
int i;
char key[N] = { '0', 'A', 'B', 'C', 'D', 'E' };//第0个元素保留不用
int w[N] = { 0, 1, 2, 4, 5, 6 }; //第0个元素保留不用
HuffTree HT;
HuffCode HC;
HuffmanCode(HT, HC, w, N - 1);
for (i = 1; i < N; i++)
printf("%c:%s\n", key[i], HC[i]);

printf("\n");
return 0;
}

 

//找出数组中权值最小的两个节点下标,分别用s1和s2保存
void select(const HuffTree &HT, int n, int &s1, int &s2)
{
int i;
s1 = s2 = 0;
int min1 = INT_MAX;//最小值，INT_MAX在<limits.h>中定义的
int min2 = INT_MAX;//次小值

for (i = 1; i <= n; ++i)
{
if (HT[i].parent == 0)
{//筛选没有父节点的最小和次小权值下标
if (HT[i].weight < min1)
{//如果比最小值小
min2 = min1;
s2 = s1;
min1 = HT[i].weight;
s1 = i;
}
else if ((HT[i].weight >= min1) && (HT[i].weight < min2))
{//如果大于等于最小值，且小于次小值
min2 = HT[i].weight;
s2 = i;
}
else
{//如果大于次小值，则什么都不做
;
}
}
}
}

//HT:哈夫曼树，HC:哈夫曼编码，w:构造哈夫曼树节点的权值，n:构造哈夫曼树节点的个数
void HuffmanCode(HuffTree &HT, HuffCode &HC, int *w, int n)
{
int s1;
int s2;
int m = 2 * n - 1; //容易知道n个节点构造的哈夫曼树是2n-1个节点
int i, c, f, j;
char *code; //暂存编码的
HT = (HuffTree)malloc((m + 1)*sizeof(HTNode)); //0单元未使用

for (i = 1; i <= n; i++)
HT[i] = { w[i], 0, 0, 0 };//初始化前n个节点(构造哈夫曼树的原始节点)

for (i = n + 1; i <= m; i++)
HT[i] = { 0, 0, 0, 0 }; //初始化后n-1个节点

//构建哈夫曼树
for (i = n + 1; i <= m; i++)
{
select(HT, i - 1, s1, s2);//找出前i-1个节点中权值最小的节点下标
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;
}
//哈夫曼编码
HC = (char **)malloc((n)*sizeof(char *));
//暂存编码
code = (char *)malloc(n*sizeof(char));//使用了第0单元
for (i = 1; i <= n; i++)
{
for (c = i, f = HT[c].parent, j = 0; f != 0; c = HT[c].parent, f = HT[c].parent, j++)
{//从叶子扫描到根
if (HT[f].lchild == c)
{
code[j] = '0';
}
else if (HT[f].rchild == c)
{
code[j] = '1';
}
else
{//否则什么也不做
;
}
}
code[j] = '\0';
HC[i] = (char *)malloc(strlen(code)*sizeof(char));
strcpy(HC[i], code);
}

}