数据结构--哈夫曼树

#include <stdio.h>

#include <string.h>

#define N 50        //叶子结点数

#define M 2*N-1     //树中结点总数

//哈夫曼树的节点结构类型

typedef struct

{

    char data;  //结点值

    double weight;  //权重

    int parent;     //双亲结点

    int lchild;     //左孩子结点

    int rchild;     //右孩子结点

} HTNode;

//每个节点哈夫曼编码的结构类型

typedef struct

{

    char cd
; //存放哈夫曼码

    int start;

} HCode;

//构造哈夫曼树

void CreateHT(HTNode ht[],int n)

{

    int i,k,lnode,rnode;

    double min1,min2;

    for (i=0; i<2*n-1; i++)         //所有结点的相关域置初值-1

        ht[i].parent=ht[i].lchild=ht[i].rchild=-1;

    for (i=n; i<2*n-1; i++)         //构造哈夫曼树

    {

        min1=min2=32767;            //lnode和rnode为最小权重的两个结点位置

        lnode=rnode=-1;

        for (k=0; k<=i-1; k++)

            if (ht[k].parent==-1)   //只在尚未构造二叉树的结点中查找

            {

                if (ht[k].weight<min1)

                {

                    min2=min1;

                    rnode=lnode;

                    min1=ht[k].weight;

                    lnode=k;

                }

                else if (ht[k].weight<min2)

                {

                    min2=ht[k].weight;

                    rnode=k;

                }

            }

        ht[i].weight=ht[lnode].weight+ht[rnode].weight;

        ht[i].lchild=lnode;

        ht[i].rchild=rnode;

        ht[lnode].parent=i;

        ht[rnode].parent=i;

    }

}

//实现哈夫曼编码

void CreateHCode(HTNode ht[],HCode hcd[],int n)

{

    int i,f,c;

    HCode hc;

    for (i=0; i<n; i++) //根据哈夫曼树求哈夫曼编码

    {

        hc.start=n;

        c=i;

        f=ht[i].parent;

        while (f!=-1)   //循序直到树根结点

        {

            if (ht[f].lchild==c)    //处理左孩子结点

                hc.cd[hc.start--]='0';

            else                    //处理右孩子结点

                hc.cd[hc.start--]='1';

            c=f;

            f=ht[f].parent;

        }

        hc.start++;     //start指向哈夫曼编码最开始字符

        hcd[i]=hc;

    }

}

//输出哈夫曼编码

void DispHCode(HTNode ht[],HCode hcd[],int n)

{

    int i,k;

    double sum=0,m=0;

    int j;

    printf("  输出哈夫曼编码:\n"); //输出哈夫曼编码

    for (i=0; i<n; i++)

    {

        j=0;

        printf("      %c:\t",ht[i].data);

        for (k=hcd[i].start; k<=n; k++)

        {

            printf("%c",hcd[i].cd[k]);

            j++;

        }

        m+=ht[i].weight;

        sum+=ht[i].weight*j;

        printf("\n");

    }

    printf("\n  平均长度=%g\n",1.0*sum/m);

}

int main()

{

    int n=8,i;      //n表示初始字符串的个数

    char str[]= {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'};

    double fnum[]= {0.07,0.19,0.02,0.06,0.32,0.03,0.21,0.1};

    HTNode ht[M];

    HCode hcd
;

    for (i=0; i<n; i++)

    {

        ht[i].data=str[i];

        ht[i].weight=fnum[i];

    }

    printf("\n");

    CreateHT(ht,n);

    CreateHCode(ht,hcd,n);

    DispHCode(ht,hcd,n);

    printf("\n");

    return 0;

}