哈夫曼树

#include <stdio.h>
#define N 50        /*叶子结点数*/
#define M 2*N-1        /*树中结点总数*/

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;

typedef struct
{
    char cd[N];        /*存放哈夫曼码*/
    int start;
} HCode;

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;
    }
}

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;
    }
}

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:",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");
    }
}

void main()
{
    int n=5,i;        /*n表示初始字符串的个数*/
    char str[]={'a','b','c','d','e'};
    double fnum[]={4,2,1,7,3};
    HTNode ht[M];
    HCode hcd[N];
    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");
}