贪心算法-Huffman算法

---

源代码

#include <stdlib.h>

#include

#include

#include

struct HtNode{

double weight;

int parent,lchild,rchild;

};

struct HtTree{

HtNode* ht;

int root;

};

typedef struct HtTree* PHtTree;

//构造有n个节点的哈夫曼树

PHtTree Huffman (int n,int* w)

{

PHtTree pht;

HtNode* ht;

//用于记录权值最小的两棵树在数组中的位置

int i,j,p1,p2;

//min1,min2用于记录两个最小的权值

double min1,min2;

//输入合法

if(n<=0) return 0;

//动态分配Haffman树的空间

//int*n=(int*)malloc(sizeof(int)*n);

pht=(HtTree*)malloc(sizeof(HtTree));

pht->ht=(HtNode*)malloc(sizeof(HtNode)*(2*n-1));

//n个叶子共有2*n-1个节点

//初始化，设置ht数组的初始值

for(i=0;i<2*n-1;i++)

{

pht->ht[i].parent=0;

if(i

{

pht->ht[i].weight=w[i];

}

else

{

pht->ht[i].weight=1000;

}

}

//执行n-1次合并操作，即构造哈夫曼树的n-1个内部节点

for(i=0;i

{

p1=p2=0;

//相关变量赋初值

min1=min2=1000;//相当于一个大数

for(j=0;j

{

if(pht->ht[j].parent==0)

{

if(pht->ht[j].weight

{ 

min1=pht->ht[j].weight;

p1=j;

}

}

}

for(j=0;j

{

if(pht->ht[j].parent==0)

{

if((pht->ht[j].weight>min1)&&(pht->ht[j].weight<=min2)&&(j!=p1))

{

min2=pht->ht[j].weight;

p2=j;

}

}

}

pht->ht[p1].parent=n+i;

pht->ht[p2].parent=n+i;

pht->ht[n+i].weight=min1+min2;

pht->ht[n+i].lchild=p1;

pht->ht[n+i].rchild=p2;

}

//返回树

return pht;

}

//计算Huffman编码

void HuffmanCode(char** HC,int n,PHtTree pht)

{

int flag;

//每个字符的编码最大长度不会超过n

//这跟树的深度有关

char*c;

//c=(char*)malloc(sizeof(char)*n);

//分配n个字符指针数组空间

//第n-1单元存储编码串的结束符

int start;

//逐个对n个字符求其哈夫曼编码

for(int i=0;i

{

flag=0;

//start=n-1;

//k,f是两个工作指针,f指向k的父亲

for(int k=i,f=pht->ht[i].parent;f!=0;k=f,f=pht->ht[k].parent)

{

flag++;

//左边分配0，右边分配1

}

//---------------

c=(char*)malloc(sizeof(char)*(flag));

c[flag]='\0';

for(int k=i,f=pht->ht[i].parent;f!=0;k=f,f=pht->ht[k].parent)

{

if(pht->ht[f].lchild==k)

{

c[--flag]='0';

}

else

{

c[--flag]='1';

}

}

//为第i个字符编码分配空间

//因为路径有长有短

HC[i]=(char*)malloc(sizeof(char));

strcpy(HC[i],c);

}

}

int main()

{

//输入

int n;

int m;

HtNode* ht;

int* weight;

char** HC;

PHtTree pht;

printf("请输入需要哈夫曼编码的节点数目\n");

scanf("%d",&n);

//分配内存空间

ht=(HtNode*)malloc(sizeof(HtNode)*n);

weight=(int*)malloc(sizeof(int)*n);

HC=(char**) malloc(sizeof(char*)*n);

printf("请输入各节点的值\n");

for(int i=0;i

{

printf("第%d个节点的权值:\n",i);

scanf("%d",&m);

weight[i]=m;

printf("\n");

}

//构造具有n个节点的Haffman树

pht=Huffman(n,weight);

HuffmanCode(HC,n,pht);

//输出编码

for(int i=0;i

{

int j=0;

printf("第%d个字符的编码,它的权值为是%d:\n",i,weight[i]);

{

printf("%s\n",HC[i]);

//j++;

}

}

return 0;

}