1120 哈夫曼树的创建遍历查找当前节点的编码

package com;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.Stack;

/**
 * 类说明:  哈夫曼树的创建遍历查找当前节点的编码
 */
public class HaffmanTree {

    TreeNode root;

    /**
     * @version 创建时间: 2017-11-21 下午8:57:01
     * 类说明:声明一个类，
     */
    public static class TreeNode<T> implements Comparable<TreeNode<T>>{
        T data;
        int weight;
        TreeNode leftChild;
        TreeNode rightNode;
        TreeNode parent;

        public TreeNode(T data, int weight) {
            super();
            this.data = data;
            this.weight = weight;
            this.leftChild = null;
            this.rightNode = null;
            this.parent = null;
        }


        @Override
        public int compareTo(TreeNode<T> o) {
            //根据weight来排序
            if(this.weight>o.weight){
                return -1;
            }else if(this.weight<o.weight){
                return 1;
            }
            return 0;
        }
    }




    /**
     * 创建haffman树
     * @param list
     * @return
     */
    public TreeNode createHaffManTree(ArrayList<TreeNode> list){
        while (list.size()>1) {
            //取最小的两个值，构建新的节点，进行排序
            Collections.sort(list);//从大到小排序
            TreeNode leftNode=list.get(list.size()-1);//取最小的值
            TreeNode rightNode=list.get(list.size()-2);//取第二小的值
            TreeNode parent=new TreeNode("data", leftNode.weight+rightNode.weight);
            parent.leftChild=leftNode;
            parent.rightNode=rightNode;
            leftNode.parent=parent;
            rightNode.parent=parent;

            list.remove(leftNode);
            list.remove(rightNode);
            list.add(parent);
        }
        //最终list里面只剩下一个元素
        root=list.get(0);
        return list.get(0);

    }

    /**
     * 遍历哈夫曼树
     * @param root
     * 思路：循环     每次取parent，取出来后，添加leftChild  rightChild
     */
    public void showHaffman(TreeNode root){
        LinkedList<TreeNode> list = new LinkedList<>();
        ArrayList<TreeNode> arrayList = new ArrayList<>();
        list.offer(root);//队列为空时候，使用add方法会报错，而offer方法会返回false,Queue使用时,才会采用 offer/poll/take等方法作为链表对象时,offer等方法相对来说没有什么意义这些方法是用于支持队列应用的。
        while(!list.isEmpty()){
            TreeNode node=list.pop();//取出栈顶元素
            System.out.print(node.data+" ");
            if(node.leftChild!=null){
                list.offer(node.leftChild);
            }
            if(node.leftChild!=null){
                list.offer(node.rightNode);
            }
        }
    }


    /**
     * 获得当前的节点编码   （左子为0  右子为1）
     * @param node
     */
    public void getCode(TreeNode node){
        Stack<String> stack = new Stack<>();
        TreeNode treeNode = node;
        while(treeNode!=null && treeNode.parent !=null){
            //left 0  right 1
            if(treeNode.parent.leftChild == treeNode){
                stack.push("0");
            }else if(treeNode.parent.rightNode == treeNode){
                stack.push("1");
            }
            treeNode=treeNode.parent;
        }
        while (!stack.isEmpty()) {
            System.out.print(stack.pop());
        }
    }



    public static void main(String[] args) {
        ArrayList<TreeNode> list = new ArrayList<>();
        TreeNode<String> node = new TreeNode("good", 54);
        list.add(node);
        list.add(new TreeNode("morning", 10));
        list.add(new TreeNode("afternoon", 20));
        list.add(new TreeNode("hello", 100));
        list.add(new TreeNode("hi", 200));
        HaffmanTree tree = new HaffmanTree();
        tree.createHaffManTree(list);
        tree.showHaffman(tree.root);
        System.out.println();
        tree.getCode(node);
    }

}

运行结果如下：

data data hi data hello data good morning afternoon 

000