基于TireTree的字典树训练编程（一）

本文背景

博主是一名正在留学的大三学生，因学校毕业要求，需要60天的工作实习，因而趁着假期，在国内的一个科技公司体验实习生活。

前几日再查资料的时候无意中看到一篇关于网易校招的Java面试题的博文，虽然时间已经有些陈旧，但是文章对我这种初出茅庐的菜鸟还是很受用的。链接如下：http://blog.youkuaiyun.com/liu_005/article/details/52267538.

看完了之后，博主开始查找资料，希望可以做一些相关联系，于是就有了下面的关于字典树的训练。

这次训练是博主第一次写字典树，也是参考了百度百科关于字典树的介绍之后才开始编写的（字典树百度百科），一定有不足的地方，希望各位前辈多多留言指教了！

字典树编程

设计

字典树第一版主要实现：插入，删除， 查询，和重置的4块功能。

效果实现

因为是练手之作，所以所有的效果实现均由console完成。

模块

模块分为3部分：字典树，字典树测试，字典树节点

代码

TireTreeNode:(字典树节点)

package tireTreeDemo;
/**
 * This is the demo for tireTree
 * @author Andy_ZhangZX
 * date(dd/mm/yy): 12/01/2018
 */
public class TireTreeNode {
	//define the parameters inside the tree node
	protected char value;
	protected TireTreeNode[] children;
	protected boolean isbuttom;
	protected int counter; // calculate how many times that the String go through this node
	
	protected final int SIZE = 26;
	
	//constructor
	public TireTreeNode(){
		this.counter = 1;
		this.children = new TireTreeNode[SIZE];
		this.isbuttom = false;
		this.value = 0;
	}
}

TireTree:(字典树)

package tireTreeDemo;
/**
 * This is the demo for tireTree
 * @author Andy_ZhangZX
 * date(dd/mm/yy): 12/01/2018
 */
public class TireTree {
	protected TireTreeNode root; //the root of the tire tree
	
	//constructor
	public TireTree(){
		root = new TireTreeNode();
	}
	
	public void insert(String string){
		int stringLength = string.length();
		TireTreeNode node = root;
		char[] letters = string.toCharArray();
		
		if(string == null || string.length() == 0) return;
		
		for(int i = 0; i < stringLength; i++){
			int position = letters[i] - 'a'; //use the ASCII code
			if(node.children[position] == null){
				node.children[position] = new TireTreeNode();//if not exist, create one
				node.children[position].value = letters[i];
			}else{
				node.children[position].counter++;//if exist, update the counter
			}
			node = node.children[position];
		}
		node.isbuttom = true;
	}
	
	public void delete(String string){
		int stringLength = string.length();
		TireTreeNode node = root;
		char[] letters = string.toCharArray();
		
		if(string == null || string.length() == 0) return;
		
		for(int i = 0; i < stringLength; i++){
			int position = letters[i] - 'a'; //use the ASCII code
			if(node.children[position].counter > 1){
				node.children[position].counter--;
			}else{
				node.children[position].counter--;
				node.children[position].value = 0;
			}
			node = node.children[position];
		}
		node.isbuttom = false;
		
	}
	
	public boolean isContain(String string,TireTree tree) throws Exception{
		try{
			TireTreeNode node = root;
			int counter = 0;
			char[] stringToArray = string.toCharArray();
			int[] stringNum = new int[string.length()];
			boolean isbuttom = false;
			
			for(int i=0;i <stringToArray.length;i++){
				stringNum[i] = stringToArray[i] - 'a'; 
			}
			

			for(int j = 0;j<stringToArray.length;j++){
				if(node.children[stringNum[j]].value == stringToArray[j]){
					isbuttom = node.children[stringNum[j]].isbuttom;
					counter++;
					node = node.children[stringNum[j]];
				}
			}
			if(counter == stringToArray.length && isbuttom == true){
				return true;
			}else{
				return false;
			}
		}catch(Exception e){
			return false; 
		}
	}
	
}

TireTreeTest：（字典树测试<main>）

package tireTreeDemo;

import java.util.Scanner;
/**
 * This is the demo for tireTree
 * @author Andy_ZhangZX
 * date(dd/mm/yy): 12/01/2018
 */

public class TireTreeTest {
	@SuppressWarnings("resource")
	public static void main(String[]args) throws Exception{
		TireTree  tree= new TireTree(); 
		initTree(tree);
		
		Scanner s  = new Scanner(System.in);
		while(true){
			String inPut = s.nextLine(); 
			String[] inputArray = inPut.split(" ");
			if(inputArray.length > 2){
				System.err.println("Wrong input");
				printUsageMessage();
			}else{
				if(inputArray[0].equals("+")){
					insertMethod(inputArray[1],tree);
				}else if(inputArray[0].equals("-")){
					deleteMethod(inputArray[1],tree);
				}else if(inputArray[0].equals("?")){
					printSearchResult(inputArray[1],searchMethod(inputArray[1],tree));
				}else if(inputArray[0].equals("~")){
					tree = resetMethod(tree);
					initTree(tree);
				}else{
					System.err.println("Wrong input");
					printUsageMessage();
				}
			}
		}
	}

	//initialize tire tree
	private static void initTree(TireTree tree){
		String[]strs= {"apple","bus","cat","dog"};
		for(String str:strs){
            tree.insert(str);
        }
	}
	
	//deleteMethod
	private static void deleteMethod(String string, TireTree tree) throws Exception{
		if(searchMethod(string,tree)){
			tree.delete(string);
		}else{
			System.err.println("The word \"" + string+"\" is not exsit!");
		}
	}
	
	//insertMethod
	private static void insertMethod(String string, TireTree tree) throws Exception{
		tree.insert(string);
	}
	
	//searchMethod
	private static boolean searchMethod(String string, TireTree tree) throws Exception{
		boolean isContain = tree.isContain(string,tree);
		if(isContain == true){
			return true;
		}else{
			return false;
		}
	}
	
	//resetMethod
	private static TireTree resetMethod(TireTree tree) throws Exception{
		tree = new TireTree();
		return tree;
	}
	
	//print Search result
	private static void printSearchResult(String string,boolean b){
		if(b == true){
			System.out.println("Word \"" + string + "\" found!");
		}else{
			System.out.println("Word \""+ string +"\" Not found!");
		}
	}
	
	//print usage message
	private static void printUsageMessage(){
		System.err.println("Usage: {op} + {SPACE} + [string]");
		System.err.println("[op] = '+' or '-' or '?' or '~'");
		System.err.println("'+' means insert, '-' means delete, '?' means search, '~' means reset");
		System.err.println("when reset the tree, command line don't need to include the string");
	}
	
}

程序操作

由于字典树的操作和效果均由控制台实现，所以用户需要在控制台输入相关的命令代码，以进行程序测试。

命令代码：

Usage: {op} + {SPACE} + [string]

[op] = '+' or '-' or '?' or '~

'+' means insert, '-' means delete, '?' means search, '~' means reset

when reset the tree, command line don't need to include the string

做添加，删除和查询的时候分别使用 ‘+’， ‘-’， ‘？’的操作符，加上空格符，再加上想要实现的字符串。

做重置的时候只需要输出‘~’操作符即可。

结果

因为根据程序，初始化树的时候用的是{"apple", "bus", "cat", "dog"} 数据， 所以在这个数据范围内就进行测试。

绿色部分为用户输入的代码指令，黑色部分为程序响应的结果。

测试一：

查询是否存在“cat”

测试二：

添加并查询 “eye”

测试三：

删除并查询 “bus”

测试四：

1.添加并查询“catch”

2.查询“cat”

3.删除“cat”

4.查询“cat”和“catch”

测试五：

1.添加并查询“fine”

2.重置字典树

3.查询“fine”

未来发展：

本作只是博主刚接触TireTree时的练手之作，定有许多不足，敬请留言指导。

后续希望能够实现整体树结构的打印，JAVAFX的可视化处理，更优化的算法以及相关的配置操作（数据库相关）。

谢谢观看，如需转载请注明出处！