[java]java实现哈夫曼编码

二叉树的结点类：该类中包含结点的基本信息，在二叉树中的位置信息以及用flag表明该结点是否参加二叉树构造

/** * @author:zym * @description:node of binary tree * @date: 2017/4/6 */public class Node {public String name;//节点符号public int weight;//权重public Node parent;public Node leftChild;public Node rightChild;public boolean flag;public StringBuffer code;public Node(String n,int w){//不同包中的类对该方法的访问权限？name = n;weight = w;flag = true;code = new StringBuffer();}@Overridepublic String toString() {return "Node [name=" + name + ", weight=" + weight + ", code=" + code + "]";}}

排序类：采用快速排序对结点权重逆序排序

/** * @author:zym * @description: include all kinds of sort method * @date: 2017/4/6 */public class Sort {public static void swap(List<Node> nodes,int i,int j){Node temp = nodes.get(i);nodes.set(i, nodes.get(j));nodes.set(j, temp);} /** * author:zym * description: quickSort of List(reverse sequence) * date:2017/4/6 */public static void quickSort(List<Node> nodes,int begin,int end){if(begin<end){Node key = nodes.get(begin);int i = begin,j = end;while(true){while(i<end&&nodes.get(i).weight>=key.weight) i++;while(j>begin&&nodes.get(j).weight<=key.weight) j--;if(i<j) swap(nodes,i,j);else break;}swap(nodes,begin,j);quickSort(nodes,begin,j-1);quickSort(nodes,j+1,end);}}}

哈夫曼编码类：构造哈夫曼二叉树并编码

/** * @author:zym * @description: data structure of huffman binary tree * @date:2017/4/6 */public class HuffmanCode {public static void createTree(List<Node> nodes){Node left = null,right = null;int k = 0,//记录下第一次遍历的断点size = nodes.size();//记录nodes的初始结点数    while(true){Sort.quickSort(nodes, 0, nodes.size()-1);for(int i=1;i<nodes.size();i++){if(nodes.get(nodes.size()-i).flag){left = nodes.get(nodes.size()-i);k = i;break;}left = null;}for(int j=k+1;j<nodes.size();j++){if(nodes.get(nodes.size()-j).flag){right = nodes.get(nodes.size()-j);break;}right = null;}if(left!=null&&right!=null){Node parent = new Node(null,left.weight+right.weight);parent.leftChild = left;parent.rightChild = right;left.parent = parent;right.parent = parent;left.flag = false;right.flag = false;nodes.add(parent);}if(nodes.size()==2*size-1){Sort.quickSort(nodes, 0, nodes.size()-1);break;}}}/** * author:zym * description: code for huffman binary tree * date: */public static void codeTree(List<Node> nodes){for(int i=1;i<nodes.size();i++){if(nodes.get(nodes.size()-i).name!=null){//查找到所有叶子结点Node temp = nodes.get(nodes.size()-i),//暂存叶子结点     temp1 = null,//暂存待编码结点     parent = null;while(true){if(temp1 == null) temp1 = temp;if(temp1.parent!=null){ parent = temp1.parent;}else break;if(parent.leftChild == temp1) temp.code.append("0");else temp.code.append("1");temp1 = parent;}//temp = nodes.get(nodes.size()-i);temp.code = temp.code.reverse();}}}}

Test类：

public class TestHuffmanCode {public static void main(String[] args){List<Node> nodes = new ArrayList<Node>();nodes.add(new Node("a",4));nodes.add(new Node("b",6));nodes.add(new Node("c",5));nodes.add(new Node("d",12));nodes.add(new Node("e",3));HuffmanCode.createTree(nodes);HuffmanCode.codeTree(nodes);for(Node node:nodes){if(node.name!=null) System.out.println(node.toString());}}}

输出结果：