Trie，字典樹

前兩天，寫了一個字典樹，感覺不太好，有點臃腫。

下面是根據網友的帖子（http://www.ej38.com/showinfo/java-184775.html，google搜索的，不曉得哪個是原創了），修改後的樣子。

package ruc.datasearch.trie;

import java.util.Iterator;
import java.util.List;

import ruc.datasearch.rule.Rule;
import ruc.datasearch.rule.Rules;

public class Trie {
	private TrieNode root;
	
	public Trie()
	{
		this.root=new TrieNode();
	}
	
	public Trie(Rules rs)
	{
		this.root=new TrieNode();
		createTrieFromRules(rs);
	}
	
	public void createTrieFromRules(Rules rs)
	{
		Iterator<Rule> iter=rs.getRules().iterator();
		try
		{
			while(iter.hasNext())
				addRule(iter.next());
		}
		finally
		{
			iter=null;
		}
	}
	
	public void addRule(Rule r)
	{
		boolean end, find;
		TrieNode node=null;
		try
		{
			node=this.root;
			for(int i=0;i<r.lhs.length();i++)
			{
				find=false;
				end=false;
				
				List<TrieNode> trieLink=node.trieLink;
				if(i==r.lhs.length()-1)
					end=true;
				
				//start to search matched character
				char ch=r.lhs.charAt(i);
				Iterator<TrieNode> iter=trieLink.iterator();
				while(iter.hasNext())
				{
					node=iter.next();
					if(node.c==ch)
					{
						find=true;
						break;
					}					
				}
				
				//if not find, then create new node
				if(!find)
				{
					TrieNode nodeTmp=new TrieNode(ch);
					trieLink.add(nodeTmp);
					node=nodeTmp;
				}
				
				//if end, then add rhs to target node
				if(end&&!node.rhsList.contains(r.rhs))
					node.rhsList.add(r.rhs);				
			}
		}
		catch(Exception e)
		{
			e.printStackTrace();
		}
		finally
		{
			node=null;
		}		
	}
	
	/**
	 * Search target list contained by target node
	 *  
	 * @param lhs
	 * @return target lhs list, this lhs list could be empty
	 */
	public List<String> searchLhsReturnList(String lhs)
	{
		TrieNode node=searchLhsReturnNode(lhs);
		if(node==null)
			return null;
		else
			return node.rhsList;
	}
	
	/**
	 * Search target node
	 * 
	 * @param lhs
	 * @return return target lhs node, this node could be null
	 */
	public TrieNode searchLhsReturnNode(String lhs)
	{
		boolean find,end;		
		TrieNode node=null;
		try
		{
			node=root;
			for(int i=0;i<lhs.length();i++)
			{
				find=false;
				end=false;
				
				if(i==lhs.length()-1)
					end=true;
				
				char ch=lhs.charAt(0);
				List<TrieNode> trieLink=node.trieLink;
								
				Iterator<TrieNode> iter=trieLink.iterator();
				while(iter.hasNext())
				{
					node=iter.next();
					if(node.c==ch)
					{
						find=true;
						break;
					}
				}
				
				if(!find)
				{
					node=null;		//if node find character in any level,then return null
					break;
				}
				if(end)				//if this is the end level, return target node
					break;
			}
			return node;
		}
		finally
		{
			node=null;
		}
	}
}

package ruc.datasearch.trie;

import java.util.LinkedList;
import java.util.List;

public class TrieNode {
	public char c;
	public LinkedList<TrieNode> trieLink;
	public List<String> rhsList;
	
	public TrieNode()
	{
		this.trieLink=new LinkedList<TrieNode>();
	}
	
	public TrieNode(char c)
	{
		this.c=c;		
		this.trieLink=new LinkedList<TrieNode>();
	}
}