构造哈夫曼树

哈夫曼编码以其高压缩比和压缩性能方面的优势一直在通信、数据压缩等领域占有重要的位置。

要实现哈夫曼编码必须先构造一棵哈夫曼树，下面就通过java进行简单的实现，通过图形化的方式展现生成哈夫曼树的全过程。

 import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.event.MouseAdapter;import java.awt.event.MouseEvent;import java.awt.geom.Ellipse2D;import java.awt.geom.Line2D;import java.util.ArrayList;import java.util.Collections;import java.util.List;import javax.swing.JFrame;import javax.swing.JPanel;public class HalfmanTree {private List<Node> collections = new ArrayList<Node>();static private boolean stop = true;public Node getRoot(){return collections.get(0);}public void add(int frequence){collections.add(new Node(frequence));}public void buildHalfmanTree(HMPanel p) throws InterruptedException{while(collections.size() > 1){Collections.sort(collections); //可以换更快速的排序方式Node m1 = collections.remove(0); //获取最小的两个元素Node m2 = collections.remove(0);Node n = new Node(m1.getFrequnce() + m2.getFrequnce());System.out.println(m1.frequnce + "+"+ m2.frequnce + "=>"+ n.frequnce);n.setLeft(m1);n.setRight(m2);m1.setParent(n);m2.setParent(n);collections.add(n);p.setRoot(n);p.repaint();while(stop)Thread.sleep(1000);stop = true;}}class Node implements Comparable<Node>{int frequnce;Node left,right,parent;public Node(int frequnce) {super();this.frequnce = frequnce;}public Node getLeft() {return left;}public void setLeft(Node left) {this.left = left;}public Node getRight() {return right;}public void setRight(Node right) {this.right = right;}public Node getParent() {return parent;}public void setParent(Node parent) {this.parent = parent;}public int getFrequnce() {return frequnce;}@Overridepublic int compareTo(Node o) {// TODO Auto-generated method stubreturn frequnce - o.frequnce;}private float x,y;public void Paint(Graphics2D g,float x,float y){g.draw(new Ellipse2D.Double(x,y,15,15));g.drawString(""+frequnce, x, y);this.x = x;this.y = y ;if(parent != null){g.draw(new Line2D.Float(x,y,parent.x, parent.y));}if(left !=null ){left.Paint(g, x - 50, y + 30);}if(left !=null ){right.Paint(g, x + 50, y + 30);}}}/** * @param args * @throws InterruptedException */public static void main(String[] args) throws InterruptedException {HalfmanTree t = new HalfmanTree();int[] nodes={ 2,5,6,7,8,9,20,40,18,13,54}; for(int n:nodes){t.add(n);}JFrame jframe = new JFrame();jframe.setBounds(100, 100, 800, 600);HMPanel p = new HMPanel(); jframe.add(p);jframe.setVisible(true);t.buildHalfmanTree(p);}static class HMPanel extends JPanel{private Node root;private int startX = 400 ,startY =10;public HMPanel(){addMouseListener(new MouseAdapter(){@Overridepublic void mouseClicked(MouseEvent e) {stop = false;}});}@Overridepublic void paint(Graphics g) {super.paint(g);if(root !=null)root.Paint((Graphics2D)g, startX, startY);}@Overridepublic void update(Graphics g) {paint(g);}public void setRoot(Node root){this.root = root;}}}