本文实例讲述了C++数据结构与算法之哈夫曼树的实现方法。，具体如下：
哈夫曼树又称最优二叉树，是一类带权路径长度最短的树。
对于最优二叉树，权值越大的结点越接近树的根结点，权值越小的结点越远离树的根结点。
前面一篇图文详解JAVA实现哈夫曼树对哈夫曼树的原理与java实现方法做了较为详尽的描述，这里再来看看C++实现方法。
具体代码如下：
#include <iostream>
using namespace std;
#if !defined(_HUFFMANTREE_H_)
#define _HUFFMANTREE_H_
/*
* 哈夫曼树结构
*/
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;
}
//建造哈夫曼树
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]=' ';
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
void 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;
}
