实验内容：

1. 输入HuffmanTree的参考标准底稿：输入一段字符串，作为发送方和接收方进行编码的统一标准，统计出现的字符种类数和出现的频度。
   2）初始化HuffmanTree参数：给定报文中26个字母a-z及空格的出现频率{64, 13, 22, 32, 103, 21, 15, 47, 57, 1, 5, 32, 20, 57, 63, 15, 1, 48, 51, 80, 23, 8, 18, 1, 16, 1, 168}。
   3）创建HuffmanTree和编码表：根据1）或2）的输入，构建赫夫曼树并为这些字符编制赫夫曼编码，并输出。
   5）模拟发送端，从键盘输入字符串，在屏幕上输出输入串的编码
   6）模拟接收端，从键盘上输入0-1赫夫曼编码串，翻译出对应的原文。

实验步骤：

（1）按照实验要求编写代码，构造赫夫曼树及其编码，体会网络发送端和接收端编码和译码过程及其工作原理。
（2）输入模拟发送端和模拟接受端的验收用例，验证其输出结果。

#include <iostream>
#include <string.h>
using namespace std;

typedef struct{
    int weight;
    int parent,lchild,rchild;
}HTNode,*HuffmanTree;

typedef char **HuffmanCode;
int n=27,s1,s2,m,i,j,count2;

void Select(HuffmanTree &HT,int end , int &s1,int &s2){
    int min1 =9999;
    int min2 = 9999;
    for(int i=1;i<=end;i++){
        if(HT[i].parent==0 && HT[i].weight<min1){
            min1 = HT[i].weight;
            s1 = i;
        }
    }
    for(int i=1;i<=end;i++){
        if(HT[i].parent == 0&&HT[i].weight<min2 &&s1!=i){
            min2 = HT[i].weight;
            s2 = i;
        }
    }
}

void CreatHuffmanTree(HuffmanTree &HT,int n){
    m = n*2-1;
    HT = new HTNode[m+1];
    for(i=1;i<=m;i++){
        HT[i].parent = 0;
        HT[i].lchild  = 0;
        HT[i].rchild = 0;
    }
    for(i=1;i<=n;i++){
        cin >> HT[i].weight;
    }
    for(i = n+1;i<=m;i++){
        Select(HT,i-1,s1,s2);
        HT[i].weight = HT[s1].weight+HT[s2].weight;
        HT[s1].parent = i;
        HT[s2].parent = i;
        HT[i].lchild = s1;
        HT[i].rchild = s2;
    }
}
void creatHuffmanCode(HuffmanTree HT,HuffmanCode &HC,int n){
    int start,c,f;
    HC  = new char*[n+1];
    char *cd = new char[n];
    cd[n-1] ='\0';
    for(int i=1;i<=n;i++){
        start = n-1;
        c = i;
        f = HT[c].parent;
        while(f!=0){
            start -- ;
            if(HT[f].lchild == c){
                cd[start]='0';
            }else {
                cd[start]='1';
            }
            c=f;
            f = HT[f].parent;
        }
        HC[i] = new char[n-start];
        strcpy(HC[i],&cd[start]);
    }
    delete cd;

}

void TransCode(HuffmanTree HT,char a[],char ch[],char b[],int n){
    count2 = 0;
    int q = 2*n-1;
    int k=0;
    for(int i=0;a[i]!='%';i++){
        if(a[i]=='0'){
            q = HT[q].lchild;
        }else if(a[i]=='1'){
            q = HT[q].rchild;
        }
        if(HT[q].lchild == 0 &&HT[q].rchild==0){
            b[k++] = ch[q-1];
            q = 2*n-1;
        }
    }
    count2=k;
    b[k]='\0';
}
int main()
{
    HuffmanTree HT;
    HuffmanCode HC;
    int count1=0;
    int code;
    char a[1000];
    char b[1000];
    char c[1000];
    char ch[27]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',' '};
    cout<<"1.输入HuffmanTree的参数"<<endl;
    cout<<"2.初始化HuffmanTree的参数(含有26字母及空格)"<<endl;
    cout<<"3.创建HuffmanTree和编码表"<<endl;
    cout<<"4.输出编码表"<<endl;
    cout<<"5.输入编码，并翻译为字符"<<endl;
    cout<<"6.输入字符，并实现转码"<<endl;
    cout<<"7.退出."<<endl;
    while(1){
        cout<<"请输入操作码："<<endl;
        cin >>code;
        if(code == 1){
            cout<<"操作完成"<<endl;
        }
        else if(code == 2){
            cout<<"请输入权值数组：";
            CreatHuffmanTree(HT,n);
            cout<<"操作完成"<<endl;
        }
        else if(code == 3){
            creatHuffmanCode(HT,HC,n);
            cout<<"操作完成"<<endl;
        }
        else if(code == 4){
            cout<<"字符"<<"\t"<<"权值"<<"\t"<<"编码"<<endl;
            for(int i=1;i<=n;i++){
                cout<<ch[i-1]<<"\t"<<HT[i].weight<<"\t"<<HC[i]<<endl;
            }
            cout<<"操作完成"<<endl;
        }
        else if(code == 5){
            cout<<"输入二进制编码(以%结束)：";
            for(i=0;i<1000;i++){
                cin >>a[i];
                char data = a[i];
                if(a[i]=='%'){
                    break;
                }
            }
            TransCode(HT,a,ch,b,n);
            cout<<"输出：";
            for(i = 0;i<count2;i++){
                cout<<b[i];
            }
            cout<<"\n操作完成"<<endl;
        }
        else if(code ==6){
            count1 = 0;
            cout<<"请输入一串字符(以%结束)：";
            for( i=0;i<1000;i++){
                cin >>c[i];
                char data = c[i];
                count1++;
                if(c[i]=='%'){
                    break;
                }
            }
            cout<<"输出：";
            for(i=0;i<count1-1;i++){
                for(j=0;j<n;j++){
                    if(c[i]==ch[j]){
                        cout<<HC[j+1];
                        break;
                    }
                }
            }
            cout<<"\n操作完成"<<endl;
        }
        else if(code == 7){
            break;
        }
    }
    return 0;
}