Huffman编码原理（C++，java实现）

对于给定一组数利用huffman对其编码

原理介绍引用自  http://www.cnblogs.com/mcgrady/p/3329825.html

1. 首先介绍huffman树

2. 首先huffman树的构建

3. Huffman编码介绍

总结：Huffman编码时一种无损压缩编码（也就是可以通过解码得到原始被压缩数据）方案

Huffman 编码是一种不等长编码，也就是说并非所有的叶子节点都位于huffman的同一个层次上

Huffman 编码通过贪心算法解决前缀问题（huffman编码是一种前缀编码）

4. c++实现

#include <iostream>#include <stdio.h>#include <vector>using namespace std;struct HuffmanNode{int left;int right;int weight;int parent;};/************************************************************************//*          寻找最小的两个数                                     *//************************************************************************///void select(HuffmanNode* pHuffmanTree,int n,int &s1,int &s2){void select(vector<HuffmanNode> pHuffmanTree,int n,int &s1,int &s2){s1=-1;s2=-1;int nMin1=-1;int nMin2=-1;for (int i=0;i<n;i++){if (pHuffmanTree[i].parent==0 && pHuffmanTree[i].weight>0){if (s1<0 || nMin1>pHuffmanTree[i].weight){s2=s1;nMin2=nMin1;s1=i;nMin1=pHuffmanTree[s1].weight;}else if (s2<0 || nMin2>pHuffmanTree[i].weight){s2=i;nMin2=pHuffmanTree[i].weight;}}}//for(int i=0;i<data_size;i++){//if(Min>data[i]){//secondMin=Min;//Min=data[i];//}else{//secondMin=data[i];//}//}}void HuffmanCoding(int *pWeight,int N, vector<vector<char>> &code){if (N<=0){return;}int m=2*N-1;//完全二叉树中节点数目比叶子节点数的2倍少1vector<HuffmanNode> pHuffmanTree(m);//表示树中有m个节点int s1,s2;/*********建立叶子节点************/for (int i=0;i<N;i++){pHuffmanTree[i].weight=pWeight[i];//相当于是Huffman树的第一层pHuffmanTree[i].parent=0;pHuffmanTree[i].left=-1;pHuffmanTree[i].right=-1;}for (int i=N;i<m;i++)//建立huffman树中除叶子节点外的其它节点{select(pHuffmanTree,i,s1,s2);pHuffmanTree[s1].parent=pHuffmanTree[s2].parent=i;pHuffmanTree[i].left=s1;pHuffmanTree[i].right=s2;pHuffmanTree[i].weight=pHuffmanTree[s1].weight+pHuffmanTree[s2].weight;}//根据建立好的Huffman树，从叶子节点到根节点计算每个叶节点的编码int node,parent;for (int i=0;i<N;i++){vector<char> &cur=code[i];node=i;parent=pHuffmanTree[node].parent;while (parent!=0){if (pHuffmanTree[parent].left==node){cur.push_back('0');} else{cur.push_back('1');}node=parent;parent=pHuffmanTree[node].parent;}reverse(cur.begin(),cur.end());}}void CalFrequency(const char* str,int* pWeight){while (*str){pWeight[*str]++;str++;}}void CalExistChar(int* pWeight,int N,vector<int>& pChar){int j=0;for (int i=0;i<N;i++){if (pWeight[i]!=0)//将存在的字符加入vector中{pChar.push_back(i);if (j!=i){pWeight[j]=pWeight[i];}j++;}}}void PrintCode(char c,vector<char> &code){cout<<(int) c<<" "<<c<<":";for (vector<char>::iterator it= code.begin();it!=code.end();it++){cout<<*it;}cout<<"\n";}void Print(vector<vector<char>>& code, vector<int>&pChar){int size=(int)code.size();for (int i=0;i<size;i++){PrintCode(pChar[i],code[i]);}}int main(){const int N=256;char str[]="Failure is probably the fortification in your pole.\It is like a peek your wallet as the thief, \when you are thinking how to spend several hard-won lepta,\when you are wondering whether new money, it has laid background.\Because of you, then at the heart of the most lax, alert,\and most low awareness, and left it godsend failed.";int pWeight[N]={0};CalFrequency(str,pWeight);pWeight['\t']=0;vector<int> pChar;CalExistChar(pWeight,N,pChar);int N2=(int)pChar.size();vector<vector<char>> code(N2);HuffmanCoding(pWeight,N2,code);Print(code,pChar);}

java实现：

package huffmanCode;import java.io.*;import java.nio.charset.StandardCharsets;import java.nio.file.Path;import java.nio.file.Paths;import java.util.ArrayList;import java.util.Collections;import java.util.List;import java.util.TreeSet;public class huffmanCode {public final int N=256;//所有AsccII有257个字符表示去除0有256public int Min,secondMin;//用来标识最小的两个数/** * read compressed file * @param filePath * @return content of text file */public static String readfile(Path filePath){List<String> linelist=Collections.emptyList(); try{linelist=java.nio.file.Files.readAllLines(filePath, StandardCharsets.UTF_8);}catch(IOException e){e.printStackTrace();}return linelist.toString();}/** * statistic the num of each char in String str * @param str * @return */public int[] countFrequency(String str){   int Num[]=new int[N];   char[] temp=str.toCharArray();   for(int i=0;i<temp.length;i++){   if(temp[i]!=0){   Num[temp[i]]++;   }   }return Num;}public ArrayList<Existchar> countExistChar(int[] Num){ArrayList<Existchar> cec=new ArrayList<Existchar>();for(int i=0;i<N;i++){if(Num[i]!=0){Existchar ec=new Existchar();ec.orgchar=(char) i;ec.num=Num[i];cec.add(ec);}}return cec;}public class Existchar{public char orgchar;public int num;public int left=0;public int right=0;public int parent=0;public String str="";}/** * toSelect the top min */public void selectTopTwoMin(ArrayList<Existchar> cec,int n){Min=-1;secondMin=-1;int Minval=Integer.MAX_VALUE;int secondMinval=Integer.MAX_VALUE;for(int i=0;i<n;i++){Existchar temp=cec.get(i);if(temp.parent==0){if(temp.num<Minval){secondMin=Min;secondMinval=Minval;Min=i;Minval=temp.num;}else if(temp.num<secondMinval){secondMin=i;secondMinval=temp.num;}}}}/** * construct Huffmantree * @param argcs */public void HuffmanCoding(ArrayList<Existchar> cec1){int N=cec1.size();int M=2*N-1;//the num of the HuffmanNodeArrayList<Existchar> cec=new ArrayList<Existchar>(M);for(int i=0;i<N;i++){cec.add(cec1.get(i));}for(int i=N;i<M;i++){selectTopTwoMin(cec,i);Existchar leftNode=cec.get(Min);Existchar rightNode=cec.get(secondMin);leftNode.parent=i;rightNode.parent=i;Existchar parentNode=new Existchar();parentNode.left=Min;parentNode.right=secondMin;parentNode.num=leftNode.num+rightNode.num;cec.add(parentNode);}for(int i=0;i<N;i++){String curstr="";Existchar curnode=cec.get(i);int parent=curnode.parent;while(parent!=0){Existchar parentNode=cec.get(parent);if(parentNode.left==i){curstr+='0';}else{curstr+='1';}parent=parentNode.parent;}curnode.str=new StringBuilder(curstr).reverse().toString();  ;cec1.set(i, curnode);}}public static void main(String argcs[]){huffmanCode code=new huffmanCode();String texPath="G://program/Java_pro/src/huffmanCode/tex.txt";String str=readfile(Paths.get(texPath));int Num[]=code.countFrequency(str);ArrayList<Existchar> cec=code.countExistChar(Num);code.HuffmanCoding(cec);for(int i=0;i<cec.size();i++){System.out.print(cec.get(i).orgchar+"\t\t\t");System.out.print(cec.get(i).str+"\n");}}}