【摘录】霍夫曼编码

 

摘录自《数据结构原理与经典问题求解》

 

 

#include <iostream>
#include "HuffmanTree.h"

using namespace std;

int main()
{
    HuffmanTree * HT = NULL;
    HuffmanCode HC;
    char Data[100];
    char *WhatLetter;
    int *Weight;
    int Count;

    cout<<"请输入一行文本数据:"<<endl;

    cin>>Data;
    cout<<endl;

    OutputWeight(Data,strlen(Data),&WhatLetter,&Weight,&Count);

    HuffmanCoding(HT, &HC, Weight, Count);

    cout<<"字符 出现频率 编码结果"<<endl;
    for(int i = 0; i<Count; i++)
    {
        cout<<WhatLetter[i]<<"     ";
        cout<<Weight[i]/1000.0<<"%\t";
        cout<<HC[i+1]<<endl;
    }
    cout<<endl;
    system("pause");
    return 0;
}

 

 

HuffmanTree.h的源代码如下

 

 

#if !defined(_HUFFMANTREE_H_)
#define _HUFFMANTREE_H_

/*
 * 霍夫曼树结构
 */
class HuffmanTree
{
public:
    unsigned int Weight;
    unsigned int Parent;
    unsigned int lChild;
    unsigned int rChild;
};

typedef char **HuffmanCode;

/*
 * 从结点集合中选出权值最小的两个结点
 * 将值分别赋给s1和s2
 */
void Select(HuffmanTree* HT,int Count,int *s1,int *s2)
{
    unsigned int temp1=0;
    unsigned int temp2=0;
    unsigned int temp3;
    for(int i=1;i<=Count;i++)
    {
        if(HT[i].Parent==0)
        {
            if(temp1==0)
            {
                temp1=HT[i].Weight;
                (*s1)=i;
            }
            else
            {
                if(temp2==0)
                {
                    temp2=HT[i].Weight;
                    (*s2)=i;
                    if(temp2<temp1)
                    {
                        temp3=temp2;
                        temp2=temp1;
                        temp1=temp3;

                        temp3=(*s2);
                        (*s2)=(*s1);
                        (*s1)=temp3;
                    }
                }
                else
                {
                    if(HT[i].Weight<temp1)
                    {
                        temp2=temp1;
                        temp1=HT[i].Weight;

                        (*s2)=(*s1);
                        (*s1)=i;
                    }
                    if(HT[i].Weight>temp1&&HT[i].Weight<temp2)
                    {
                        temp2=HT[i].Weight;
                        (*s2)=i;
                    }
                }
            }
        }
    }
}

/*
 * 霍夫曼编码函数
 */
void HuffmanCoding(HuffmanTree * HT,
                   HuffmanCode * HC,
                   int *Weight,
                   int Count)
{
    int i;
    int s1,s2;
    int TotalLength;
    char* cd;
    unsigned int c;
    unsigned int f;
    int start;

    if(Count<=1) return;
    TotalLength=Count*2-1;
    HT = new HuffmanTree[(TotalLength+1)*sizeof(HuffmanTree)];

    for(i=1;i<=Count;i++)
    {
        HT[i].Parent=0;
        HT[i].rChild=0;
        HT[i].lChild=0;
        HT[i].Weight=(*Weight);
        Weight++;
    }
    for(i=Count+1;i<=TotalLength;i++)
    {
        HT[i].Weight=0;
        HT[i].Parent=0;
        HT[i].lChild=0;
        HT[i].rChild=0;
    }

    //建造霍夫曼树
    for(i=Count+1;i<=TotalLength;++i)
    {
        Select(HT, i-1, &s1, &s2);
        HT[s1].Parent = i;
        HT[s2].Parent = i;
        HT[i].lChild = s1;
        HT[i].rChild = s2;
        HT[i].Weight = HT[s1].Weight + HT[s2].Weight;
    }

    //输出霍夫曼编码
    (*HC)=(HuffmanCode)malloc((Count+1)*sizeof(char*));
    cd = new char[Count*sizeof(char)];
    cd[Count-1]='\0';
    for(i=1;i<=Count;++i)
    {
        start=Count-1;
        for(c = i,f = HT[i].Parent; f != 0; c = f, f = HT[f].Parent)
        {
            if(HT[f].lChild == c)
                cd[--start]='0';
            else
                cd[--start]='1';
            (*HC)[i] = new char [(Count-start)*sizeof(char)];
            strcpy((*HC)[i], &cd[start]);
        }
    }

    delete [] HT;
    delete [] cd;
}

/*
 * 在字符串中查找某个字符
 * 如果找到，则返回其位置
 */
int LookFor(char *str, char letter, int count)
{
    int i;
    for(i=0;i<count;i++)
    {
        if(str[i]==letter) return i;
    }
    return -1;
}

void OutputWeight(char *Data,int Length,char **WhatLetter,int **Weight,int *Count)
{
    int i;
    char* Letter = new char[Length];
    int* LetterCount = new int[Length];
    int AllCount=0;
    int Index;
    int Sum=0;
    float Persent=0;

    for(i=0;i<Length;i++)
    {
        if(i==0)
        {
            Letter[0]=Data[i];
            LetterCount[0]=1;
            AllCount++;
        }
        else
        {
            Index=LookFor(Letter,Data[i],AllCount);
            if(Index==-1)
            {
                Letter[AllCount]=Data[i];
                LetterCount[AllCount]=1;
                AllCount++;
            }
            else
            {
                LetterCount[Index]++;
            }
        }
    }
    for(i=0;i<AllCount;i++)
    {
        Sum=Sum+LetterCount[i];
    }

    (*Weight) = new int[AllCount];
    (*WhatLetter) = new char[AllCount];

    for(i=0;i<AllCount;i++)
    {
        Persent=(float)LetterCount[i]/(float)Sum;
        (*Weight)[i]=(int)(1000*Persent);
        (*WhatLetter)[i]=Letter[i];
    }
    (*Count)=AllCount;

    delete [] Letter;
    delete [] LetterCount;
}

#endif