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参考自：http://blog.csdn.net/jdhanhua/article/details/6621026
哈夫曼树
哈夫曼树（霍夫曼树）又称为最优树.
1、路径和路径长度
在一棵树中，从一个结点往下可以达到的孩子或孙子结点之间的通路，称为路径。通路中分支的数目称为路径长度。若规定根结点的层数为1，则从根结点到第L层结点的路径长
2、结点的权及带权路径长度
若将树中结点赋给一个有着某种含义的数值，则这个数值称为该结点的权。结点的带权路径长度为：从根结点到该结点之间的路径长度与该结点的权的乘积。
3、树的带权路径长度
树的带权路径长度规定为所有叶子结点的带权路径长度之和，记为WPL。
代码一（树节点）：
/** * 树节点 * * @author pang * * @param <T> */ public class Node<T> implements Comparable<Node<T>> { private T data; private int weight; private Node<T> left; private Node<T> right; public Node(T data, int weight) { this.data = data; this.weight = weight; } @Override public String toString() { // TODO Auto-generated method stub return "data:" + this.data + ",weight:" + this.weight + "; "; } @Override public int compareTo(Node<T> o) { // TODO Auto-generated method stub if (o.weight > this.weight) { return 1; } else if (o.weight < this.weight) { return -1; } return 0; } public T getData() { return data; } public void setData(T data) { this.data = data; } public int getWeight() { return weight; } public void setWeight(int weight) { this.weight = weight; } public Node<T> getLeft() { return left; } public void setLeft(Node<T> left) { this.left = left; } public Node<T> getRight() { return right; } public void setRight(Node<T> right) { this.right = right; } }
代码二（HuffmanTree）:
import java.util.ArrayList; import java.util.Collections; import java.util.LinkedList; import java.util.List; import java.util.Queue; public class HuffmanTree<T> { public static <T> Node<T> createTree(List<Node<T>> nodes) { while (nodes.size() > 1) { Collections.sort(nodes); Node<T> left = nodes.get(nodes.size() - 1); Node<T> right = nodes.get(nodes.size() - 2); Node<T> parent = new Node<T>(null, left.getWeight() + right.getWeight()); parent.setLeft(left); parent.setRight(right); nodes.remove(left); nodes.remove(right); nodes.add(parent); } return nodes.get(0); } public static <T> List<Node<T>> breath(Node<T> root) { List<Node<T>> list = new ArrayList<Node<T>>(); Queue<Node<T>> queue = new LinkedList<>(); queue.add(root); while (!queue.isEmpty()) { Node<T> pNode = queue.poll(); list.add(pNode); if (pNode.getLeft() != null) { queue.add(pNode.getLeft()); } if (pNode.getRight() != null) { queue.add(pNode.getRight()); } } return list; } }
测试类：
import java.util.ArrayList; import java.util.List; public class HuffmanTreeTest { public static void main(String[] args) { // TODO Auto-generated method stub List<Node<String>> nodes = new ArrayList<Node<String>>(); nodes.add(new Node<String>("b", 5)); nodes.add(new Node<String>("a", 7)); nodes.add(new Node<String>("d", 2)); nodes.add(new Node<String>("c", 4)); Node<String> root = HuffmanTree.createTree(nodes); System.out.println(HuffmanTree.breath(root)); } }
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原文地址：http://www.cnblogs.com/huadoumi/p/5266165.html
