演算法是準確的，目前程式還有一點點小bug

public class HTNode
{
	String name;                             // name of node
	int  weight;                               //weight
	int parent;                               //parent node
	int lchild;                               //leftchild node
	int rchild;                               //rightchild node	
	String Hcode;                              //huffman code
}
 

/**
 * this program is to show how HuffmanTree work.
 * to create huffmantree,and to huffmancode.
 * @author NEU 小宇
 * @version1.0
 */
public class Huffman 
{
	
	public HTNode[] ht;
	
	public static final int LEAF_NODE_NUM = 6;
	
	public Huffman()
	{
		ht = new HTNode[2*LEAF_NODE_NUM - 1];        //to initialize an array of nodes   
		for(int i = 0; i < 2*LEAF_NODE_NUM - 1; i++)
			ht[i] = new HTNode();
		ht[0].weight = 5;
		ht[1].weight = 8;
		ht[2].weight = 15;
		ht[3].weight = 30;
		ht[4].weight = 17;
		ht[5].weight = 27;
		ht[0].name = "a";
		ht[1].name = "b";
		ht[2].name = "c";
		ht[3].name = "d";
		ht[4].name = "e";
		ht[5].name = "f";
	}
	
	public void createHuffman()
	{
		int i, j, k, lnode, rnode;
		int min1, min2;
		
		for(i = 0; i < 2*LEAF_NODE_NUM - 1; i++)
			ht[i].parent = ht[i].lchild = ht[i].rchild = -1;
		for(i = LEAF_NODE_NUM; i < 2*LEAF_NODE_NUM - 1 ; i++)
		{
			min1 = min2 = 32767;
			lnode = rnode = -1;
			for(k = 0; k <= i - 1; k++){
				if(ht[k].parent == -1)
				{
					if(ht[k].weight < min1)
					{
						min2 = min1;
						rnode = lnode;
						min1 = ht[k].weight;
						lnode = k;
					}
					else if(ht[k].weight < min2)
					{
						min2 = ht[k].weight;
						rnode = k;
					}
				}
			}
				System.out.println(lnode+ "  " + rnode);
				ht[lnode].parent = i;
				ht[rnode].parent = i;
				ht[i].weight = ht[lnode].weight + ht[rnode].weight;
				ht[i].lchild = lnode;
				ht[i].rchild = rnode;
		}
	}
	void CreateHCode(HTNode[] ht)
	{
		for(int i = 0; i < LEAF_NODE_NUM; i++ )
		{
			int f = ht[i].parent;
			int c = i;
			while(f != -1)
			{
				if(ht[f].lchild == c)
					ht[i].Hcode = "0" + ht[i].Hcode;
				else
					ht[i].Hcode = "1" + ht[i].Hcode;
				c = f;
				f = ht[f].parent;
			}
		}
	}
}
 

import java.util.Scanner;

/**Input the sting, 
 * then you'll get the Huffman code
 * 
 * @author NEU 小宇
 * @version1.0
 */
public class GetHuffmanCode              
{
	public static void main(String[] args)
	{
		Huffman huffman = new Huffman();
		huffman.createHuffman();
		huffman.CreateHCode(huffman.ht);
		for(int i = 0; i < 6; i++)
			System.out.print(huffman.ht[i].Hcode + "   ");
		Input(huffman);
	}
	public static void Input(Huffman hf)
	{
		System.out.println("Input string(5 letters of a,b,c,d,e,f):");
		Scanner scanner = new Scanner(System.in);
		String inputStr = scanner.next();
		String subStr;
		for(int i = 0; i < 5; i++)
		{
			subStr = inputStr.substring(i, i + 1);
			if(subStr.equals("a"))
				System.out.print(hf.ht[0].Hcode);
			else if(subStr.equals("b"))
				System.out.print(hf.ht[1].Hcode);
			else if(subStr.equals("c"))
				System.out.print(hf.ht[2].Hcode);
			else if(subStr.equals("d"))
				System.out.print(hf.ht[3].Hcode);
			else if(subStr.equals("e"))
				System.out.print(hf.ht[4].Hcode);
			else if(subStr.equals("f"))
				System.out.print(hf.ht[5].Hcode);
		}
	}
}