huffman编码
这里随便写了个用java实现的哈夫曼编码的算法（二叉树表示）。
/**
*@(#)岑村高科
*/
package cn.javayy.struct;
/**
*定义了一种接口，要进行编码的最小单元类必需实现些接口
*@authorboss
*
*createon:下午10:56:592009-5-19
*/
publicinterface Combinable<T> extends Comparable<T> {
T combinate(T a,T b);
}
=====================================================================================
/**
*@(#)岑村高科
*/
package cn.javayy.struct;
/**
*thehuffmantreeClass
*<p>哈夫曼树，包括当前节点数据信息，左节点，右节点信息。
*@authorboss
*
*createon:下午10:16:232009-5-19
*/
publicclass HuffmanTree<T extends Combinable<T>> implements Comparable<HuffmanTree<T>>{
/**therootofhuffmantree*/
private T root;
/**theleftnodeofhuffmantree*/
private HuffmanTree<T> left;
/**therightnodeofhuffmantree*/
private HuffmanTree<T> right;
/**哈夫曼编码字符串，如:0000110*/
private String huffmanCodeString = "";
/**是否对最终生成的哈夫曼进行过编码操作*/
privatestaticbooleanisSettedHuffmanCoderString = false;
public T getRoot() {
returnroot;
}
publicvoid setRoot(T root) {
this.root = root;
}
public HuffmanTree<T> getLeft() {
returnleft;
}
publicvoid setLeft(HuffmanTree<T> left) {
this.left = left;
}
public HuffmanTree<T> getRight() {
returnright;
}
publicvoid setRight(HuffmanTree<T> right) {
this.right = right;
}
/**
*重写此方法用于递归合并节点后进行排序操作
*/
@Override
publicint compareTo(HuffmanTree<T> o) {
// TODO Auto-generated method stub
return o.getRoot().compareTo(this.getRoot());
}
@Override
public String toString(){
return"the root:" + this.getRoot()
+ "\r\nthe left:" + this.getLeft()
+ "\r\nthe right:" + this.getRight();
}
/**
*对最终生成的树进行哈夫曼编码，使每个叶子节点生成01的路径编码
*/
privatevoid setHuffmanCoderString(){
HuffmanTree<T> left = this.getLeft();
//如果有左节点则在路径中追加"0"
if(left != null){
left.huffmanCodeString = this.huffmanCodeString + "0";
left.setHuffmanCoderString();//递归编码
}
HuffmanTree<T> right = this.getRight();
//如果有右节点则在路径中追加"1"
if(right != null){
right.huffmanCodeString = this.huffmanCodeString + "1";
right.setHuffmanCoderString();//递归编码
}
}
publicvoid printHuffmanCoderString(){
//打印最终生成树的哈夫曼编码前要进行编码操作，
//且此操作只执行一次，所以用全局标识变量判断
if(!HuffmanTree.isSettedHuffmanCoderString){
this.setHuffmanCoderString();
HuffmanTree.isSettedHuffmanCoderString = true;//标识已执行过编码
}
//如果是叶子节点（即要编码的单元），则打印出编码信息，如果是非叶子结点（中间临时生成的节点），则不打印
if(this.left == null && this.right == null)
System.out.println("the " + this.getRoot() + " huffmanCoder:" + this.huffmanCodeString);
if(this.left != null)
this.left.printHuffmanCoderString();//递归打印
if(this.right != null)
this.right.printHuffmanCoderString();//递归打印
}
}
===================================================================================
/**
*@(#)岑村高科
*/
package cn.javayy.struct;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
/**
*用类用于生成一个哈夫曼树
*@authorboss
*
*createon:下午10:51:392009-5-19
*/
publicclass HuffmanTreeFactory<T extends Combinable<T>> {
/**初始时一个list列表当作要编码的单元类的容器*/
private List<HuffmanTree<T>> HuffmanTreeCollection;
// public HuffmanTreeFactory(){}
/**
*@paramunitClasses待编码的单元类集合
*/
public HuffmanTreeFactory(List<T> unitClasses){
if(unitClasses == null || unitClasses.size() == 0)
thrownew IllegalArgumentException("the unit classes collection can't be empty");
HuffmanTreeCollection = new LinkedList<HuffmanTree<T>>();
//初始化哈夫曼集合容器
for(T unitClass : unitClasses){
HuffmanTree<T> huffmanTree = new HuffmanTree<T>();
huffmanTree.setRoot(unitClass);
huffmanTree.setLeft(null);
huffmanTree.setLeft(null);
HuffmanTreeCollection.add(huffmanTree);
}
Collections.sort(HuffmanTreeCollection);
}
/**
*将待编码的哈夫曼集合处理成只含有一个元素的集合，则这最后一个元素
*即为最终生成的哈夫曼树
*/
privatevoid generateHuffmanTree(){
while(true){
if(HuffmanTreeCollection == null || HuffmanTreeCollection.size() <= 1)
break ;
//处理之前一定要重新排序，这是哈夫曼编码的关键原理
Collections.sort(HuffmanTreeCollection);
HuffmanTree<T> huffmanTreeOne = HuffmanTreeCollection.remove(0);
HuffmanTree<T> huffmanTreeTwo = HuffmanTreeCollection.remove(0);
HuffmanTree<T> huffmanTreeNew = new HuffmanTree<T>();
//将集合中前面两个元素合并成一个元素插到集合中去
//并将第一个元素和第二个元素分别作为新元素的左，右节点
huffmanTreeNew.setRoot(huffmanTreeOne.getRoot().combinate(huffmanTreeOne.getRoot(), huffmanTreeTwo.getRoot()));
huffmanTreeNew.setLeft(huffmanTreeOne);
huffmanTreeNew.setRight(huffmanTreeTwo);
HuffmanTreeCollection.add(huffmanTreeNew);
}
}
/**
*
*@return生成最终的哈夫曼树
*/
public HuffmanTree<T> getHuffmanTree(){
generateHuffmanTree();
returnthis.HuffmanTreeCollection.get(0);
}
}
========================================================================
/**
*@(#)岑村高科
*/
package cn.javayy.struct;
import java.io.Serializable;
/**
*自定义一个用于测试的单元类
*@authorboss
*
*createon:下午09:53:072009-5-19
*/
publicclass UnitClass implements Serializable,Combinable<UnitClass>{
/**
*serialVersionUID
*/
privatestaticfinallongserialVersionUID = -4109190579335512743L;
/**出现概率数据*/
privateintrate;
public UnitClass(int rate){
this.rate = rate;
}
publicint getRate() {
returnrate;
}
publicvoid setRate(int rate) {
this.rate = rate;
}
/**
*implementsthidcompartTo()inordertosortthecollectionstoredfromunitclass
*/
@Override
publicint compareTo(UnitClass o) {
return o.getRate() > this.rate ? 1: o.getRate() < this.rate ? -1 : 0;
}
@Override
public String toString(){
return"the rate is:" + rate;
}
/**
*重写此方法用于哈夫曼编码时可以合并两个分支点信息
*/
@Override
public UnitClass combinate(UnitClass a, UnitClass b) {
if(a == null || b == null)
returnnull;
returnnew UnitClass(a.getRate() + b.getRate());
}
}
======================================================================
/**
*@(#)岑村高科
*/
package cn.javayy.struct;
import java.util.ArrayList;
import java.util.List;
/**
*@authorboss
*
*createon:下午10:03:122009-5-19
*/
publicclass Main {
publicstaticvoid main(String[] args){
List<UnitClass> l = new ArrayList<UnitClass>();
l.add(new UnitClass(2));
l.add(new UnitClass(4));
l.add(new UnitClass(10));
l.add(new UnitClass(7));
l.add(new UnitClass(20));
HuffmanTreeFactory<UnitClass> factory = new HuffmanTreeFactory<UnitClass>(l);
// System.out.println(factory.getHuffmanTree());
factory.getHuffmanTree().printHuffmanCoderString();
}
}
===========================================================================
打印结果：
the the rate is:20 huffmanCoder:0
the the rate is:10 huffmanCoder:10
the the rate is:2 huffmanCoder:1100
the the rate is:4 huffmanCoder:1101
the the rate is:7 huffmanCoder:111
