构建哈夫曼树

一、哈夫曼树也叫赫夫曼树，是一颗权值路径最小的二叉树。

   我们用的测试数据是 ：{6,32,15,21,3,43,69,52,39,70};

二、构建完的树如下图：

三、代码实现

package com.cn.test.tree;

import java.util.*;

public class HalfManTree {

    public static void main(String[] args) {
        //构建哈夫曼树的节点
        int[] data = {6,32,15,21,3,43,69,52,39,70};
        System.out.println("原始的数据:"+ Arrays.toString(data));
        //构建
        HalfManTreeNode halfManTreeNode = HalfManTreeNode(data);
        //构建完之后的root节点
        System.out.println("构建完之后的root节点:"+halfManTreeNode);
        System.out.print("先序打印哈夫曼树树：");
        prePrint(halfManTreeNode);
        //打印每一个页节点的路径值
        System.out.println();
        prePrintRoute(halfManTreeNode, "");
        //找出某一个值的路径
        System.out.println("查询一个特定值的路径。。。。。。。。。。。。。");
        int key = 39;
        String route = prePrintRouteByValue(halfManTreeNode, "", key);
        System.out.println(key+"的路径是："+route);
    }



    public static HalfManTreeNode HalfManTreeNode(int[] data){
        if(data == null){
            return null;
        }
        //1、把数组元素构建成节点
        List list = new ArrayList();
        for(int d:data){
            list.add(new HalfManTreeNode(d));
        }
        System.out.println("节点list:"+list);

        while (list.size()>1){
            Collections.sort(list);
            HalfManTreeNode leftNode = list.get(0);
            HalfManTreeNode rightNode = list.get(1);
            HalfManTreeNode parentNode = new HalfManTreeNode(leftNode.getValue()+rightNode.getValue());
            parentNode.setLeftNode(leftNode);
            parentNode.setRightNode(rightNode);
            list.remove(0);
            list.remove(0);
            list.add(parentNode);
        }
        return list.get(0);
    }

    /**
     * 前序打印树
     * @param halfManTreeNode
     */
    public static void prePrint(HalfManTreeNode halfManTreeNode){
        if(halfManTreeNode == null){
            return;
        }
        System.out.print(halfManTreeNode.getValue()+" ");
        if(halfManTreeNode.getLeftNode()!=null){
            prePrint(halfManTreeNode.getLeftNode());
        }
        if(halfManTreeNode.getRightNode()!=null){
            prePrint(halfManTreeNode.getRightNode());
        }
    }

    /**
     * 打印每一个元素的路径
     * 向左是0，右是1
     * @param halfManTreeNode
     */
    public static void prePrintRoute(HalfManTreeNode halfManTreeNode,String route){
        if(halfManTreeNode == null){
            return;
        }

        if(halfManTreeNode.getRightNode() == null && halfManTreeNode.getLeftNode() == null){
            System.out.println(halfManTreeNode.getValue()+" 路径是 "+ route);
        }

        if(halfManTreeNode.getLeftNode()!=null){
             prePrintRoute(halfManTreeNode.getLeftNode(),route+"0");
        }
        if(halfManTreeNode.getRightNode()!=null){
             prePrintRoute(halfManTreeNode.getRightNode(),route+"1");
        }
    }

    /**
     * 前序打印树
     * @param halfManTreeNode
     */
    public static String prePrintRouteByValue(HalfManTreeNode halfManTreeNode,String route,int value){
        if(halfManTreeNode == null){
            return null;
        }

        if(halfManTreeNode.getRightNode() == null && halfManTreeNode.getLeftNode() == null && halfManTreeNode.getValue() == value){
            return route;
        }

        if(halfManTreeNode.getRightNode() == null && halfManTreeNode.getLeftNode() == null){
            return null;
        }

        if(halfManTreeNode.getLeftNode()!=null){
            String s = prePrintRouteByValue(halfManTreeNode.getLeftNode(), route + "0", value);
            if(s!=null){
                return s;
            }
        }
        if(halfManTreeNode.getRightNode()!=null){
            String s = prePrintRouteByValue(halfManTreeNode.getRightNode(), route + "1", value);
            if(s!=null){
                return s;
            }
        }
        return null;
    }
}

class HalfManTreeNode implements Comparable{
    private  int value;
    private HalfManTreeNode leftNode;
    private HalfManTreeNode rightNode;

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

    public int getValue() {
        return value;
    }

    public void setValue(int value) {
        this.value = value;
    }

    public HalfManTreeNode getLeftNode() {
        return leftNode;
    }

    public void setLeftNode(HalfManTreeNode leftNode) {
        this.leftNode = leftNode;
    }

    public HalfManTreeNode getRightNode() {
        return rightNode;
    }

    public void setRightNode(HalfManTreeNode rightNode) {
        this.rightNode = rightNode;
    }

    @Override
    public String toString() {
        return "HalfManTreeNode{" +
                "value=" + value +
                '}';
    }

    @Override
    public int compareTo(HalfManTreeNode o) {
        return this.value - o.value;
    }
}

四、打印结果：

原始的数据:[6, 32, 15, 21, 3, 43, 69, 52, 39, 70]
节点list:[HalfManTreeNode{value=6}, HalfManTreeNode{value=32}, HalfManTreeNode{value=15}, HalfManTreeNode{value=21}, HalfManTreeNode{value=3}, HalfManTreeNode{value=43}, HalfManTreeNode{value=69}, HalfManTreeNode{value=52}, HalfManTreeNode{value=39}, HalfManTreeNode{value=70}]
构建完之后的root节点:HalfManTreeNode{value=350}
先序打印哈夫曼树树：350 141 70 71 32 39 209 88 43 45 21 24 9 3 6 15 121 52 69 
70 路径是 00
32 路径是 010
39 路径是 011
43 路径是 100
21 路径是 1010
3 路径是 101100
6 路径是 101101
15 路径是 10111
52 路径是 110
69 路径是 111
查询一个特定值的路径。。。。。。。。。。。。。
39的路径是：011