標准Trie字典樹學習二：Java實現方式之一

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系列文章：

1. 標准Trie字典樹學習一：原理解析

2. 標准Trie字典樹學習二：Java實現方式之一

 

 

Trie樹基於Java的一種簡單實現， 上代碼。

 

1. 定義節點類TrieNode

/**
 * TrieNode 節點類
 * @author Konrad created on 2017/10/28
 */
public class TrieNode {
    private LinkedList<TrieNode> children;  //子節點
    private char data; //節點字符
    private int freq; //頻率
    boolean isEnd;  //是否為葉子節點

    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. 定義Trie樹類TrieTree

/**
 * TrieTree Trie樹類
 *
 * @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) {...}

    //查找返回節點
    public TrieNode searchNode(String word) {...}

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

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

    //獲取詞頻
    public int getFreq(String word) {...}
}

 

 3. 插入節點

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.查找節點

//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;
    }

//查找返回節點
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.刪除節點

//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.獲取某個詞的頻率

 //獲取詞頻
    public int getFreq(String word) {
        TrieNode trieNode = searchNode(word);
        if(null != trieNode){
            return trieNode.getFreq();
        }else{
            return 0;
        }
    }

 

7.代碼測試

/**
 * @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); //插入節點，構建Trie樹
        }

        //判斷是否存在
        System.out.println("Does the word 'facebook' exists: " + trieTree.search("facebook"));
        //統計do的詞頻
        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"));
    }
}

 

輸出結果：

　　

 

 

 這只是Trie樹的實現方法之一，也可以使用其他不同方式來實現。