哈夫曼树学习笔记 Java实现

<span style="font-size:18px;">package DataStructureAndAlgorithm.Tree;/** * 哈夫曼树结构：data结点数值；left、right：左子树、右子树；weight：结点权重 * @author zhen * * @param <T> */public class Huffman<T> {private Object data;private double weight;private Huffman<T>left;private Huffman<T>right;public Huffman(Object data, double weight) {super();this.data = data;this.weight = weight;}@Overridepublic String toString() {return "Huffman [data=" + data + ", weight=" + weight + ", left=" + left + ", right=" + right + "]";}public Object getData() {return data;}public void setData(Object data) {this.data = data;}public double getWeight() {return weight;}public void setWeight(double weight) {this.weight = weight;}public Huffman<T> getLeft() {return left;}public void setLeft(Huffman<T> left) {this.left = left;}public Huffman<T> getRight() {return right;}public void setRight(Huffman<T> right) {this.right = right;}}</span>

<span style="font-size:18px;">package DataStructureAndAlgorithm.Tree;import java.util.ArrayDeque;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.List;import java.util.Queue;/** * 用哈夫曼算法构造的扩充二叉树称为哈夫曼编码树or哈夫曼树 * 哈夫曼算法： * 1、用给定的一组权值{w1，w2 ... wn}，生成一个有n棵树组成的森林F={T1，T2， ... Tn}，其中每棵二叉树Ti只有一个结点，即权值为wi的根节点（也是叶子） * 2、从F中选择两棵根结点权值最小的树，作为新树根的左、右子树，新树根的权值是左、右子树根结点的权值之和 * 3、从F中删除这两棵树，并将新二叉树加入F中 * 4、重复（2）（3），直至F中只包含一棵树为止 *  * 哈夫曼树主类：createHuffmanTree：创建哈夫曼树；breadthFirst：宽度优先遍历 * @author zhen * */public class HuffmanTree {@SuppressWarnings({ "unchecked", "rawtypes" })public static <T> Huffman<T> createHuffmanTree(List<Huffman<T>>huffmans){if(huffmans==null||huffmans.size()==0){return null;}if(huffmans.size()==1){return huffmans.get(0);}while(huffmans.size()>1){Collections.sort(huffmans,new SortHuffman());Huffman<T>left=huffmans.get(huffmans.size()-1);Huffman<T>right=huffmans.get(huffmans.size()-2);Huffman<T>parent=new Huffman<T>(null, left.getWeight()+right.getWeight());parent.setLeft(left);parent.setRight(right);huffmans.remove(left);huffmans.remove(right);huffmans.add(parent);}return huffmans.get(0);}public static <T> List<Huffman<T>> breadthFirst(Huffman<T>root){if(root==null){return null;}List<Huffman<T>>list=new ArrayList<>();Queue<Huffman<T>>queue=new ArrayDeque<>();queue.offer(root);while(!queue.isEmpty()){list.add(queue.peek());Huffman<T> parent=queue.poll();if(parent.getLeft()!=null){queue.offer(parent.getLeft());}if(parent.getRight()!=null){queue.offer(parent.getRight());}}return list;}}class SortHuffman<T> implements Comparator<Huffman<T>>{@Overridepublic int compare(Huffman<T> o1, Huffman<T> o2) {return o1.getWeight()>o2.getWeight()?-1:o1.getWeight()<o2.getWeight()?1:0;}}</span>

<span style="font-size:18px;">//测试类package DataStructureAndAlgorithm.Tree;import java.util.ArrayList;import java.util.List;public class HuffManMain {public static <T> void main(String[] args) {List<Huffman<T>> list = new ArrayList<>();list.add(new Huffman<T>("a", 9));list.add(new Huffman<T>("b", 11));list.add(new Huffman<T>("c", 13));list.add(new Huffman<T>("d", 3));list.add(new Huffman<T>("e", 5));list.add(new Huffman<T>("f", 12));Huffman<T> root = HuffmanTree.createHuffmanTree(list);System.out.println(HuffmanTree.breadthFirst(root));}}</span>

参考：http://blog.csdn.net/jdhanhua/article/details/6621026，《数据结构——C++语言描述》