赫夫曼树的实现

package HuffmanTrere;

import javax.swing.plaf.nimbus.NimbusLookAndFeel;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

public class HuffmanTree {
    public static void main(String[] args) {
   int arr []={13,7,8,3,29,6,1};
   Node root=createHuffmanTree(arr);
   preOrder(root);
    }
    public static void preOrder(Node root){
        if(root!=null){
            root.preOrder();

        }
        else {
            System.out.println("是空树，不能遍历");
        }
    }
    public static Node createHuffmanTree(int []arr){
        List<Node> nodes=new ArrayList<Node>();
        for(int value :arr){
            nodes.add(new Node(value));

        }
        while (nodes.size()>1) {
            //排序从小到大
            Collections.sort(nodes);
            System.out.println("nodes" + nodes);
            //取出权值最小的数
            Node leftNode = nodes.get(0);
            //取出权值第二小的数
            Node rightNode = nodes.get(1);
            //构建一颗二叉树
            Node parentNode = new Node(leftNode.value + rightNode.value);
            parentNode.right = rightNode;
            parentNode.left = leftNode;
            //从array中删除处理过的二叉树
            nodes.remove(leftNode);
            nodes.remove(rightNode);
            nodes.add(parentNode);

        }
        return nodes.get(0);
        //返回赫尔曼夫的root根节点
    }
}
class Node implements Comparable<Node> {
    int value; //结点的权值。
    Node left;  //左指针
    Node right; //右指针
    public void preOrder(){
        System.out.println(this);
        if(this.left!=null){
            this.left.preOrder();
        }
        if(this.right!=null){
            this.right.preOrder();
        }
    }

    public Node(int value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "Node [value=" + value + "]";
    }

    @Override
    public int compareTo(Node o) {
        return this.value - o.value; //表示从小到大排序
    }
}