c++实现哈夫曼树，哈夫曼编码，哈夫曼解码（字符串去重，并统计频率）

#include <iostream>
#include <iomanip>
#include <string>
#include <cstdlib>
using namespace std;

//定义哈夫曼树存储结构
typedef struct
{
    char data;    //存放结点数据
    int weight;      //记录结点权值
    int parent, lchild, rchild;
}HTNode, * HuffmanTree;

//哈夫曼编码存储表示
typedef char** HuffmanCode;    //动态分配数组储存哈夫曼编码表

//初始化
HuffmanTree InitHuffman(HuffmanTree& HT, int n)
{
    if (n < 0)
    {
        cout << "输入初态结点数目不正确！！！" << endl;
        return NULL;
    }
    else
    {
        int m = 2 * n - 1;            //n个叶子结点的哈夫曼树有2n-1个结点
        HT = new HTNode[m + 1];        //0号单元未用，申请m+1个空间
        for (int i = 1; i <= m; i++)
        {
            HT[i].parent = 0;
            HT[i].lchild = 0;
            HT[i].rchild = 0;
            HT[i].weight = 0;
            HT[i].data = '-';
        }

        //输入初始数据，为了方便理解HT[0]不存放数据
        cout << "请输入初态结点数据及相应权值（格式形式：a 3）：";
        for (int i = 1; i <= n; i++)
        {
            cin >> HT[i].data;
            cin >> HT[i].weight;
        }
        return HT;
    }
}

//打印HT
void PrintState(HuffmanTree& HT, int n)
{
    int m = 2 * n - 1;  //总结点数
    cout << "结点i	data值	weight	parent	lchild	rchild" << endl;
    for (int i = 1; i <= m; i++)
    {
        cout << setw(3) << i << "	";
        cout << setw(4) << HT[i].data << "	";
        cout << setw(4) << HT[i].weight << "	";
        cout << setw(4) << HT[i].parent << "	";
        cout << setw(4) << HT[i].lchild << "	";
        cout << setw(4) << HT[i].rchild << "	" << endl;
    }
}

//选择双亲域为0且两权值最小的结点，选择范围为1到i-1
int* Select(HuffmanTree& HT, int n, int* Idx)
{
    int MIN, MinSecond;
    //打擂台法使权最小值和次权最小值最大（假设第一个值权值最小无法进行）
    MIN = MinSecond = 99999;
    //循环从1到n次
    for (int i = 1; i <= n; i++)
    {
        //如果双亲为0（未删除结点与新生成结点），一定会执行if语句,寻找权最小值
        if ((HT[i].parent == 0) && HT[i].weight < MIN)
        {
            //将最小的权值给MinSecond方便寻找次最小值
            MinSecond = MIN;
            MIN = HT[i].weight;
            //记录权最小值下标
            Idx[0] = i;
        }
        //否则如果满足条件寻找次最小值
        else if ((HT[i].parent == 0) && HT[i].weight < MinSecond)
        {
            MinSecond = HT[i].weight;
            //记录权次最小值下标
            Idx[1] = i;
        }

    }
    return Idx;
}

//构造哈夫曼树
void CreateHuffmanTree(HuffmanTree& HT, int n)
{
    if (n <= 1)
        return;

    int m = 2 * n - 1;        //n个叶子结点的哈夫曼树有2n-1个结点
    //从n+1开始构造哈弗曼树
    for (int i = n + 1; i <= m; i++)
    {
        //Idx用于存放两个返回最小权值的下标，i-1为前n个结点，后面随着i增加，n也增加
        int* Idx = Idx = new int[2];
        Idx = Select(HT, i - 1, Idx);
        int s1 = Idx[0];   //权最小值下标
        int s2 = Idx[1];   //权次最小值下标
        //给两权值最小的结点置双亲,使s1，s2结点不在录入Select范围
        HT[s1].parent = i;
        HT[s2].parent = i;

        //给新节点i左右孩子置位s1,s2
        HT[i].lchild = s1;
        HT[i].rchild = s2;

        //给新结点赋权值
        HT[i].weight = HT[s1].weight + HT[s2].weight;
        delete[]Idx;
    }
}

//哈夫曼编码
void CreateHuffmanCode(HuffmanTree& HT, HuffmanCode& HC, int n)
{
    HC = new char* [n + 1];            //分配字符的空间
    char* TempCode = new char[n];    //分配临时编码表空间n个
    TempCode[n - 1] = '';            //编码有叶子结点开始逆序存放，先将末尾结束符标志打上，为后序strcpy
    //for循环逐个逆序求叶子结点的哈夫曼编码
    for (int i = 1; i <= n; i++)
    {
        int start = n - 1;            //开始存放的起点指向末尾，用于后面HC拷贝是的起始地址
        int NodeIdx = i;            //NodeIdx最开始存放叶子结点序号
        int ParentsIdx = HT[i].parent;    //Parents指向其双亲结点序号
        //若有双亲则由下到上进行编码，编码的字符，从序号1开始
        while (ParentsIdx)
        {
            start--;                //在一维数组末尾，strat先指向最后
            //若双亲结点的左结点序号为NodeIdx，将0打入一维临时数组中，否则打入1
            if (HT[ParentsIdx].lchild == NodeIdx)
                TempCode[start] = '0';
            else
                TempCode[start] = '1';
            //结点的序号更新，进入上一层
            NodeIdx = ParentsIdx;
            ParentsIdx = HT[NodeIdx].parent;
        }
        //临时一维数组存放编码成功，开始用HC顺序存放字符编码
        HC[i] = new char[n - start];        //为序号为i的字符分配编码空间
        strcpy_s(HC[i], n - start, &TempCode[start]);    //编码字符串拷贝strcpy报错因为没有指定长度
    }
    //打印哈夫曼编码
    cout << "---字符对应编码----" << endl;
    for (int i = 1; i <= n; i++)
    {
        cout << HT[i].data << "		" << HC[i] << endl;
    }
    delete []TempCode;
}

//输入字符打印哈夫曼编码
void PrintCode(HuffmanTree & HT, HuffmanCode & HC, int n)
{
    char *str =new char[100];    //存储需要解码的字符
    int flag = 0;                //flag用于检查输入是否错误
    cout << "请输入需要编码的字符：";
    cin >> str;
    //匹配字符并打印相应的哈夫曼编码
    cout << "输入的字符哈夫曼编码为：";
    for (int j = 0; j < strlen(str); j++)
    {
        flag = 0;
        for (int i = 1; i <= n; i++)
        {
            //匹配成功打印编码
            if (HT[i].data == str[j])
            {
                cout << HC[i] ;
                flag = 1;            //匹配成功
            }
        }
        //如果有匹配失败的情况，则跳出循环
        if (flag == 0)
        {
            cout << "
第" << j+1 << "字符输入错误!" ;
            break;
        }
        
    }
    putchar(10);    
    delete []str;        //释放str空间
}

//哈夫曼解码并打印
void HuffmanDecode(HuffmanTree& HT, int n)
{
    char* str = new char[1024];
    cout << "请输入二进制编码：";
    cin >> str;

    int flag = 0;    //用于检查二进制编码是否输入错误
    cout << "解码对应字符为：";
    //遍历二进制编码
    for (int i = 0; i < strlen(str);)
    {
        int Root = 2 * n - 1;    //Root为根结点序号
        //当结点的左右孩子不为空时进入循环，由根结点进入
        while (HT[Root].lchild && HT[Root].rchild)
        {
            if (str[i] == '0')
                Root = HT[Root].lchild;
            else if (str[i] == '1')
                Root = HT[Root].rchild;
            else
            {
                cout << "输入的二级制编码有误！" << endl;
                flag = 1;
                break;
            }
            i++;        //相后读取二进制编码，i值更新
        }
        //如果找到错误跳出循环
        if (flag)
            break;
        //打印编码对应字符
        cout << HT[Root].data;
    }
    delete []str;
}

int main()
{
    int n;
    cout << "请输入哈夫曼树初态结点数：";
    cin >> n;

    //初始化哈夫曼树
    HuffmanTree HT = InitHuffman(HT, n);
    //打印HT初态
    cout << "--------------------HT初态--------------------" << endl;
    PrintState(HT, n);
    //构造哈夫曼树
    CreateHuffmanTree(HT, n);
    //打印HT终态
    cout << "--------------------HT终态--------------------" << endl;
    PrintState(HT, n);

    HuffmanCode HC;
    //哈夫曼编码-由下而上
    CreateHuffmanCode(HT, HC, n);
    //打印字符对应编码
    PrintCode(HT, HC, n);
    //哈夫曼解码并打印-由上而下
    HuffmanDecode(HT, n);

    return 0;
}

//由于编译器版本原因strcpy出现不安全原因，导致无法运行，后使用strcpy_s给予拷贝长度得到解决；把“==”写成“=”导致报错；
/*
输入字符串统计字符个数（权值）
int CreateWeightArray(char* str, int* Array) {
//初始化权值数组，128为str[i]的最大数值
for (int i = 0; i < 128; i++)
{
Array[i] = 0;
}

int length = 0;

//利用下标记录位权
for (int i = 0; str[i]; i++)
{
Array[str[i]]++; //值加1，下标即字符
}
//统计字符串去重后的长度
for (int i = 0; i < 128; i++)
{
if (Array[i] != 0)
{
length++;
}
}
return length;
}
*/