构造哈夫曼树

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;
}
@Override
public int compareTo(Node o) {
// TODO Auto-generated method stub
return 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(){
@Override
public void mouseClicked(MouseEvent e) {
stop = false;
}

});
}

@Override
public void paint(Graphics g) {
super.paint(g);
if(root !=null)
root.Paint((Graphics2D)g, startX, startY);

}
@Override
public void update(Graphics g) {
paint(g);
}

public void setRoot(Node root){
this.root = root;
}

}
}