package com.atguigu.huffmancode;import com.sun.org.glassfish.external.statistics.CountStatistic;
import com.sun.org.glassfish.external.statistics.StringStatistic;import java.util.*;/*** @创建人 wdl* @创建时间 2021/3/27* @描述*/
public class HuffmanCode {public static void main(String[] args) {String content="i like like like java do you like a java";byte[] contentBytes = content.getBytes();System.out.println(contentBytes.length);//40List<Node> nodes = getNodes(contentBytes);System.out.println(nodes);//测试一把，创建的二叉树System.out.println("赫夫曼树");Node huffmanTreeRoot = createHuffmanTree(nodes);System.out.println("前序遍历");huffmanTreeRoot.preOrder();//测试一把是否生成了对应的赫夫曼编码getCodes(huffmanTreeRoot,"",stringBuilder);System.out.println("生成的赫夫曼编码表"+huffmanCodes);}//生成赫夫曼树对应的赫夫曼编码//思路：//1.将赫夫曼编码表存放在Map<Byte,String>形式static Map<Byte,String> huffmanCodes= new HashMap<Byte,String>();// 32->01 97->100...//2.在生成赫夫曼编码表示，需要去拼接璐姐，定义一个StringBuilder存储某个叶子结点的路径static  StringBuilder stringBuilder=new StringBuilder();/*** 功能：将传入的node节点的所有叶子节点的赫夫曼编码的到，并放入到huffmanCodes集合* @param node  传入节点* @param code 路径：左子节点是0，右子节点是1* @param stringBuilder 是用于拼接路径*/private static void getCodes(Node node,String code,StringBuilder stringBuilder){StringBuilder stringBuilder2 = new StringBuilder(stringBuilder);//将code加入到stringBuild2stringBuilder2.append(code);if(node!=null){//如果node==null不处理//判断当前node是叶子结点还是非叶子节点if(node.data==null){//非叶子节点//递归处理//向左getCodes(node.left,"0",stringBuilder2);//向右getCodes(node.right,"1",stringBuilder2);}else {//说明是一个叶子结点//表示找到了某个叶子节点的最后huffmanCodes.put(node.data,stringBuilder2.toString());}}}//前序遍历的方法private static void preOrder(Node root){if(root!=null){root.preOrder();}else {System.out.println("赫夫曼树为空");}}/**** @param bytes 接收字节数组* @return 返回的就是List形式*/private static List<Node> getNodes(byte[] bytes){//1.创建一个ArrayListArrayList<Node> nodes = new ArrayList<>();//遍历bytes 统计每一个byte出现的次数->map[key,value]HashMap<Byte, Integer> counts = new HashMap<>();for(byte b:bytes){Integer count=counts.get(b);if (count==null){//map中还没有这个字符数据，第一次counts.put(b,1);}else {counts.put(b,count+1);}}//把每一个键值对转成Node对象，并加入到nodes集合//遍历mapfor(Map.Entry<Byte,Integer> entry:counts.entrySet()){nodes.add(new Node(entry.getKey(),entry.getValue()));}return nodes;}//可以通过List创建对应的赫夫曼树private static Node createHuffmanTree(List<Node> nodes){while (nodes.size()>1){//排序,从小到大Collections.sort(nodes);//取出第一颗最小的二叉树Node leftNode = nodes.get(0);//取出第二颗最小的二叉树Node rightNode = nodes.get(1);//创建一颗新的二叉树，它的根节点没有data，只有权值Node parent=new Node(null,leftNode.weight+rightNode.weight);parent.left=leftNode;parent.right=rightNode;//将已经处理的两颗二叉树从nodes删除nodes.remove(leftNode);nodes.remove(rightNode);//将新的二叉树，加入到nodesnodes.add(parent);}//nodes最后的节点，就是哈夫曼树的根节点return nodes.get(0);}}//创建Node，待数据和权值
class Node implements Comparable<Node>{Byte data;//存放数据(字符)本身，比如'a'=>97 ' '=>32int weight;//权值，表示字符出现的次数Node left;Node right;public Node(Byte data, int weight) {this.data = data;this.weight = weight;}@Overridepublic int compareTo(Node o) {//从小到大排序return this.weight-o.weight;}@Overridepublic String toString() {return "Node{" +"data=" + data +", weight=" + weight +'}';}//前序遍历public void preOrder(){System.out.println(this);if(this.left!=null){this.left.preOrder();}if (this.right!=null){this.right.preOrder();}}}