字典树Trie学习二：Java实现方式之一

Posted 2020-10-12 To Be A BIG Man!

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　　博文主要是学习过程中的知识整理，以便之后的查阅回顾。部分内容来源于网络（如有摘录未标注请指出）。内容如有差错，也欢迎指正！

 

系列文章：

1. 标准Trie字典树学习一：原理解析

2. 标准Trie字典树学习二：Java实现方式之一

 

 

Trie树基于Java的一种简单实现， 上代码。

 

1. 定义节点类TrieNode

/**
 * TrieNode 节点类
 * @author Konrad created on 2017/10/28
 */
public class TrieNode {
    private LinkedList<TrieNode> children;  //子节点
    private char data; //节点字符
    private int freq; //频率
    boolean isEnd;  //是否为叶子节点

    public TrieNode(char data){
        this.children = new LinkedList<>();
        this.freq = 0;
        this.isEnd = false;
        this.data = data;
    }

    public TrieNode childNode(char c){
        if(null != children){
            for(TrieNode child : children){
                if(child.getData() == c){
                    return child;
                }
            }
        }
        return null;
    }


    public LinkedList<TrieNode> getChildren() {
        return children;
    }

    public void setChildren(LinkedList<TrieNode> children) {
        this.children = children;
    }

    public char getData() {
        return data;
    }

    public void setData(char data) {
        this.data = data;
    }

    public int getFreq() {
        return freq;
    }

    public void setFreq(int freq) {
        this.freq = freq;
    }

    public void addFreq(int step){
        this.freq += step;
    }

    public void subFreq(int step){
        this.freq -= step;
    }

    public boolean isEnd() {
        return isEnd;
    }

    public void setEnd(boolean end) {
        isEnd = end;
    }
}

 

2. 定义Trie树类TrieTree

/**
 * TrieTree Trie树类
 *
 * @author Konrad created on 2017/10/28
 */
public class TrieTree {
    private TrieNode root;

    public TrieTree() {
        this.root = new TrieNode(\' \');
    }

    //查找是否存在
    public boolean search(String word) {...}

    //查找返回节点
    public TrieNode searchNode(String word) {...}

    //插入
    public void insert(String word) {...}

    //移除
    public void remove(String word) {...}

    //获取词频
    public int getFreq(String word) {...}
}

 

 3. 插入节点

public void insert(String word) {
        TrieNode current = root;
        for (int i = 0; i < word.length(); i++) {
            TrieNode child = current.childNode(word.charAt(i));
            if (null != child)
                current = child;
            else {
                current.getChildren().add(new TrieNode(word.charAt(i)));
                current = current.childNode(word.charAt(i));
            }
            current.addFreq(1);
        }
        current.setEnd(true);
    }

 

 4.查找节点

//查找是否存在
public boolean search(String word) {
        TrieNode current = root;
        for (int i = 0; i < word.length(); i++) {
            if (null == current.childNode(word.charAt(i)))
                return false;
            else
                current = current.childNode(word.charAt(i));
        }

        if (current.isEnd())
            return true;
        else
            return false;
    }

//查找返回节点
public TrieNode searchNode(String word) {
        TrieNode current = root;
        for (int i = 0; i < word.length(); i++) {
            if (null == current.childNode(word.charAt(i)))
                return null;
            else
                current = current.childNode(word.charAt(i));
        }

        if (current.isEnd())
            return current;
        else
            return null;
    }

 

 5.删除节点

//移除
public void remove(String word) {
        if (!search(word))
            return;

        TrieNode current = root;
        for (char c : word.toCharArray()) {
            TrieNode child = current.childNode(c);
            if (child.getFreq() == 1) {
                current.getChildren().remove(child);
                return;
            }else{
                child.subFreq(1);
                current = child;
            }
        }
        current.setEnd(false);
    }

 

6.获取某个词的频率

 //获取词频
    public int getFreq(String word) {
        TrieNode trieNode = searchNode(word);
        if(null != trieNode){
            return trieNode.getFreq();
        }else{
            return 0;
        }
    }

 

7.代码测试

/**
 * @author Konrad created on 2017/10/28
 */
public class TrieTreeDemo {
    public static void main(String[] args) {
        String sentence = "today is good day what is you name at facebook how do you do what are you doing here";
        TrieTree trieTree = new TrieTree();
        for (String str : sentence.split(" ")) {
            trieTree.insert(str); //插入节点，构建Trie树
        }

        //判断是否存在
        System.out.println("Does the word \'facebook\' exists: " + trieTree.search("facebook"));
        //统计do的词频
        System.out.println("Frequent of the word \'you\': " + trieTree.getFreq("do"));

        //移除today
        System.out.println("Does the word \'today\' exists - before remove: " + trieTree.search("today"));
        trieTree.remove("today");
        System.out.println("Does the word \'today\' exists - after remove: " + trieTree.search("today"));
    }
}

 

输出结果：

　　

 

 

 这只是Trie树的实现方法之一，也可以使用其他不同方式来实现。