数据结构—哈夫曼编码应用

落日映苍穹つ 2022-08-23 08:58 144阅读 0赞

## 构造一棵哈夫曼树，输出对应的哈夫曼编码和平均查找长度。并用表7.8所示的数据进行验证。 ##

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代码：

#include <iostream>
    #include <malloc.h>
    #include <string.h>
    #define M 2*N-1
    #define N 50
    typedef char ElemType;
    using namespace std;
    typedef struct
    {
        char data[N];     //节点值
        double weight;  //权值
        int parent;    //双亲节点
        int lchild;    //左孩子节点
        int rchild;    //右孩子节点
    } HTNode;
    
    typedef struct
    {
        char cd[N];   //存放当前节点的哈夫曼编码
        int start;    //cd[start]~cd[n]存放哈夫曼编码
    } HCode;
    
    void CreateHT(HTNode ht[],int n)
    {
        int i,k,lnode,rnode;
        double min1,min2;
        for (i=0; i<2*n-1; i++)         
            ht[i].parent=ht[i].lchild=ht[i].rchild=-1;
        for (i=n; i<2*n-1; i++)         
        {
            min1=min2=32767;            
            lnode=rnode=-1;
            for (k=0; k<=i-1; k++)
                if (ht[k].parent==-1)  
                {
                    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++) 
        {
            hc.start=n;
            c=i;
            f=ht[i].parent;
            while (f!=-1)              
            {
                if (ht[f].lchild==c)    
                    hc.cd[hc.start--]='0';
                else                   
                    hc.cd[hc.start--]='1';
                c=f;
                f=ht[f].parent;
            }
            hc.start++;     
            hcd[i]=hc;
        }
    }
    
    void DispHCode(HTNode ht[],HCode hcd[],int n)
    {
        int i,k;
        double sum=0,m=0;
        int j;
        cout<<"  输出哈夫曼编码:\n"; 
        for (i=0; i<n; i++)
        {
            j=0;
            cout<<"      "<<ht[i].data<<":\t";
            for (k=hcd[i].start; k<=n; k++)
            {
                cout<<hcd[i].cd[k];
                j++;
            }
            m+=ht[i].weight;
            sum+=ht[i].weight*j;
            cout<<endl;
        }
        cout<<"\n  平均长度="<<1.0*sum/m<<endl;
    }
    
    int main()
    {
        int n=15,i;      
        char *str[]= {"The","of","a","to","and","in","that","he","is","at","on","for","His","are","be"};
        double fnum[]= {1192,677,541,518,462,450,242,195,190,181,174,157,138,124,123};
        HTNode ht[M];
        HCode hcd[N];
        for (i=0; i<n; i++)
        {
            strcpy(ht[i].data,str[i]);
            ht[i].weight=fnum[i];
        }
        cout<<endl;
        CreateHT(ht,n);
        CreateHCode(ht,hcd,n);
        DispHCode(ht,hcd,n);
        cout<<endl;
        return 0;
    }

运行结果：  
![Center 1][]

[Center]: /images/20220721/c84c7a872d934afea16d899cdfb445e8.png
[Center 1]: /images/20220721/dab9bb1d30e64c109616795b79a553d8.png